Class 9

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Tamilnadu Samacheer Kalvi 9th English Expressing Views on a Given Picture

Tips on Views on Pictures

1. Understand the picture
2. Identity the theme
3. Bring out the causes
4. Suggest a remedy
5. Write about ten sentences with coherence
6. Give a title

Exercises
Look, at the picture given below. Express your views on it in about five sentences :
1.

Answer:
1. In the picture depicts the wastage of water.
2. The tap is opened and the water is over flouring from a bucket.
3. At every place, people are suffering from water scarcity.
4. So, it is our duty to avoid wastage of water.
5. We should create awareness on saving water among others.

2.

Answer:
1. In the given picture, two persons are practicing Silambaattam.
2. It is a martial art form, practiced from the days of the Tamil kings.
3. It has metamorphosed into a non-violent form of folk dance, adding stepping styles into the dance to the measure of time.
4. This martial art form also teaches the performer the methods of self-defense.
5. Silambam was banned in Tamil Nadu during the British rule. Britishers viewed this martial art as a potential threat in the face of revolts.

3.

Answer:
Circus
1. It seems to be a circus.
2.1 want to visit the circus.
3.1 can see a ring of fire in the picture.
4.1 can see mickey mouse with balloons.
5. I’ll enjoy a lot if I go there.
6. Generally children will have a lot of fun there.

4.

Answer:
Railway Platform
1. This is a scene on a railway platform.
2. We see passengers alighting the train with their luggage.
3. More of them are waiting to board it.
4. The passengers are standing before a sleeper class compartment.
5. Yet boarding and alighting will be more convenient if the passengers queue up.

You can Download Samacheer Kalvi 9th English Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

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Tamilnadu Samacheer Kalvi 9th English Unknown Poem Paraphrase

Exercises
Read the poem given below and complete its paraphrase with suitable phrases in the given blanks :

1. I love to rise in a summer mom,
When the birds sing on every tree;
The distant huntsman winds his home,
And the sky-lark sings with me.
O! what sweet company!
But to go to school in a summer mom,
O!’ it drives all joy away;
Under a cruel eye outworn
The little ones spend the day,
In sighing and dismay.

– William Blake

Paraphrase:
I like to wake up on a …………..(i)………….. when the birds …………..(ii)………….. The distant …………..(iii)………….. has already gone on his hunting. The skylark sings happily. Everything is happy around me. The thought of going to …………..(iv)………….. drives all joy away. The children spend their time …………..(v)………….. in the classroom, supervises by an old teacher. They are dismayed at the instructions that do not give them joy.
Answer:
(i) summer morning
(ii) sing on every tree
(iii) huntsman
(iv) school in a summer morning
(v) in sighing and dismay

2. Little drops of water
Little grains of sand
Make the mighty ocean
And the pleasant land
Little deeds of kindness,
Little words of love,
Make the earth and Eden
Like the heaven above
And the little moments
Humble thoughts they be
Make the mighty ages
of eternity.

Paraphrase :
Little drops …………..(i)………….. make the might ocean …………..(ii)………….. of sand make the pleasant land. Little deeds of …………..(iii)………….. make the earth and even like (iv) The little moments and humble thoughts make the mighty …………..(v)…………..
Answer:
(i) of water
(ii) Little grains
(iii) Kindness and little words of love
(iv) the haven above
(v) ages of eternity

3. If you can’t be a banyan on
The top of the hill
Be a scrub in the plain but be
The best little scrub by the side of the hill;
Be a bush if you can’t be a tree.
If you can’t be a bush be a bit of the grass,
And some highway you will happier make;
If you can‘t be a lotus then just be a bass
But the liveliest bass in the lake!

Paraphrase:
The poet tells the readers not to …………..(i)………….. because of their positions in life. Though one can’t be a banyan tree on top of the hill, one can still be the best …………..(ii)………….. One can at least be a …………..(iii)………….. if not a tree. If one can’t be a …………..(iv)………….. one can be grass or a lotus. If one can’t even be a lotus, then one can just be a bass and be the …………..(v)………….. bass in the lake.
Answer:
(i) be worry
(ii) little scrub by the side of the hill
(iii) bush
(iv) tree
(v) liveliest

4. I took a piece of plastic clay
And idly fashioned it, one day,
And as my fingers pressed it, still
It moved and yielded to my will
I came again when days were passed
That bit of clay was hard at last
The form I gave it, still it bore,
And I could change that form no more.

Paraphrase :
The artist took a piece of …………..(i)………….. He pressed it with …………..(ii)………….. It moved and gave into …………..(iii)………….. Finally, he molded it into a statue and went away. He returned after many days. The clay was now …………..(iv)………….. It still bore the form he had given. But he …………..(v)………….. that form no more.
Answer:
(i) plastic clay
(ii) his fingers
(iii) his will
(iv) hard
(v) could change

You can Download Samacheer Kalvi 9th English Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

Exploring the textbook concepts is not enough for students who dreamt to do a cakewalk in English grammar. Consistently do your learning and practicing session with Samacheer Kalvi 9th English Grammar study material and achieve all your dreams.

Tamilnadu Samacheer Kalvi 9th English Diary Writing

Exercises
Write a Diary Entry

1. Write a diary entry in 60-80 words describing your thoughts about Water Scarcity.
Answer:

Diary Entry About Water Scarcity

12-10-2018, Friday
9.30 p.m.

Dear diary,
People are suffering due to water scarcity everywhere. Do you know the reasons for water scarcity? It is mainly because of excess population growth and mismanagement of water resources. Inefficient use of water for agriculture is prevalent everywhere. ’ Traditional water recharging areas are reduced due to the rapid construction of residential and commercial buildings. Sewage and waste water drainage management is not properly implemented. These sewage-disposal lines are connected to water bodies. Chemicals and effluents are dumped into rivers, streams, and ponds. De-silting operations in large water bodies like dams, lakes, ponds are not being carried out at proper timings. Hence water storage capacity during monsoon is not enhanced. All these problems should be solved.

Rajan.

2. Write a diary entry in 60-80 words describing your thoughts about the Effect of an Earthquake.
Answer:

Diary Entry About The Effect Of Earthquake

29-09-2018, Saturday
9.30 p.m.

Dear diary,
Today an earthquake hit the Indonesian city of Palu. The Richter magnitude scale of the earthquake is 7.7 and 384 people had been killed and the death toll was expected to rise. Most deaths are caused by the collapse of structures and the construction practices also play a major part in the death toll of an earthquake. Other effects such as landslides, soil liquefaction, and tsunamis have also played an important role in destruction produced by earthquakes.

3. Write a diary entry in 60-80 words describing your thoughts about Union is Strength.
Answer:

Diary Entry About Union Is Strength

14-08-2018, Tuesday
9.30 p.m.

Dear diary,
The topic that I am going to talk about is “Union is Strength.” In a word, unity means oneness or togetherness. When there is oneness there is likely to be more strength in opinion, more strength in action and more strength in character. For example: if you take a stick, it could break easily. But when you take a bundle of sticks, it is hard to break. This is the unique power of unity. One very good example is this Elocution Contest. All the Rotarians are united in their stand. They work hard to make this elocution contest a success. Unity among the various races is vital for the progress of the nation as the saying goes; “United we Stand, Divided we Fall”.

Rajesh.

You can Download Samacheer Kalvi 9th English Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

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Tamilnadu Samacheer Kalvi 9th English Completion of Dialogues (Fill in type)

Exercises
Complete the following dialogue appropriately :
1. Selvi : (i) _________?
Librarian : Yes, Come in. (ii) _________?
Selvi : I wish to become a member of the library.
Librarian You have to pay a membership fee.
Selvi : (iii) _________?
Librarian : An annual fee of two hundred rupees.
Selvi : (iv) _________?
Librarian : You can borrow four books at a time.
Selvi : (v) _________?
Librarian : You should return the books within fifteen days.
Answer:
(i) May I come in sir
(ii) What can I do for you?
(iii) How much should I pay?
(iv) How many books can I borrow at a time?
(v) When should I return the books?

2. Bookseller Hello Sir! (1) __________?
Customer Sir, would you allow me to exchange this book with another book?
Bookseller (ii) __________?
Customer A few pages are missing in this book.
Bookseller (iii) __________?
Customer I bought the book this morning.
Bookseller (iv) __________?
Customer : Here is the bill (v) __________?
Am:
(i) May I help you
(ii) Is something wrong with this book
(iii) When did you buy it
(iv) Do you have the biu
(v) and the book. Kindly exchange it

3. (Telephonic Conversation)
Rm : Hello (i) __________?
Rahim : Yes, may I know who is calling?
Ram : (ii) __________?
Rahim : Hi Ram, what can I do for you?
Ram : (iii) __________? Are you free after six this evening?
Rahim : Sorry. Ram (iv) __________? Will it be convenient for you to come tomorrow morning.
Ram : Ok (v) __________?
Answer:
(i) Is Mr. Rahim at home
(ii) It’s Ram. May I see you for five minutes
(iii) It’s an important personal matter
(iv) I have an urgent appointment with my boss
(v) See you tomorrow at 9 a.m.

4. TTR : Ticket please.
Traveller : Sorry sir, somehow I have lost my ticket.
TTR : (i) ________ ?
Traveller : (ii) ________?
TTR : Then (iii) ________?
Traveller : Just a minute sir (iv) ________?
TTR : Be quick.
Traveller : I got it. Here it is sir.
TTR : (v) ________?
Traveller : OK. Thank you sir.
Answer:
(i) Then you have to take a new ticket with penalty.
(ii) I don’t have enough money to take another ticket sir.
(iii) Then, what are you going to do?
(iv) Shall I check once again in my bags?
(v) 0k. Always keep your ticket at safe place. Don’t waste others time.

You can Download Samacheer Kalvi 9th English Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

Exploring the textbook concepts is not enough for students who dreamt to do a cakewalk in English grammar. Consistently do your learning and practicing session with Samacheer Kalvi 9th English Grammar study material and achieve all your dreams.

Tamilnadu Samacheer Kalvi 9th English Dialogue Writing

Exercises
1. Write a dialogue between a customer and a shop keeper.
Answer:
Customer : Good morning sir.
Shop Keeper : Good morning. What do you want?
Customer : I want an LED TV.
Shop Keeper : Which brand do you like, sir?
Customer : I want Philips TV.
Shop Keeper : What features do you want in it?
Customer : I want 40 inches along with 3D provision.
Shop Keeper : Here it is, sir. It costs Rs. 50,000/-.
Customer : Could I pay the money through debit card?
Shop Keeper : Yes sir. May I pack this for you?
Customer : Yes.

2. Write a dialogue with a minimum five utterances between a doctor and a patient who complains of stomachache.
Answer:
Patient : Good morning, doctor. I have stomach ache.
Doctor : Good morning. Since when?
Patient : From yesterday, doctor.
Doctor : Did you eat oily food from some platform stalls?
Patient : Yes doctor. I took non-veg items from a platform shop.
Doctor : The pain is due to bacterial infection. Take these tablets and tonic twice a day after food.
Patient : O.K. doctor. How much is the bill amount?
Doctor : It is Rs. 200. Take care of your health.
Patient : Thank you doctor.

3. Write a dialogue between you and your mother about the upcoming food carnival in your school.
Answer:
Daughter : Mummy, there will be a food carnival in our school.
Mother : Oh, It is very nice. When will it be organized?
Daugher : Coming weekend Mummy.
Mother : Do you know who are the participants?
Daughter : My teacher told that around 100 students of classes XI and XII would participate.
Mother : What type of food will they prepare? .
Daughter : They will prepare national and international delicacies that represent various states.
Mother : Will there be fast food stalls?
Daughter : Definitely such stalls will not be allowed. Only traditional food items will be prepared by them.
Mother : That is very good.
Daughter : My teacher instructed that each and every student should bring their parents to the carnival, Mummy.

4. WrIte a dialogue with at least 5 utterances between the manager of a restaurant and an angry customer who finds a fly in his soup.
Answer:
Waiter : Here’s your soup, Sir.
Customer : Thank you. (tastes the hot soup). What’s this? Eek! A fly in my soup. (shouts) Waiter! No, I’d better talk to the manager.
Manager : Is something wrong?
Customer : It is the soup that is wrong.
Manager : What happened, sir?
Customer : I ordered for a vegetarian soup but ¡ was served a non-veg soup.
Manager : A non-veg. soup? In this hotel?
Customer : Yes, certainly. See this.
Manager : Oh, I’m extremely sorry. Waiter, get him another bowl of soup.
Customer : Oh, no, thank you, not another non-veg. soup.

5. Write a dialogue with at least five utterances between a bank manager and a student who wants to open a bank account.
Answer:
Student : Good morning sir, I wish to open a Savings Bank account.
Banker : Good morning. Go through this application, please.
Student : Application seeks information about my address, occupation and income details.
Banker : Yes. Please fill it.
Student : How much should I deposit initially?
Banker : You should deposit at least 500/- If you need a cheque book, you have to maintain a minimum balance of 1000/-
Student : Should I produce any documents?
Banker : Yes, bring a xerox copy of your ration card and you need to give two passport size photos. An account holder of this bank should give a letter of introduction.
Student : Sure, Sir. Thank you.
Banker : Come with all the necessary papers and meet the clerk.
Student : 0k sir, Thank you!

You can Download Samacheer Kalvi 9th Science Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 13 Chemical Bonding

Samacheer Kalvi 9th Science Chemical Bonding Textbook Exercises

I. Choose the correct answer.

Question 1.
Number of valence electrons in carbon is …………….
(a) 2
(b) 4
(c) 3
(d) 5
Answer:
(b) 4

Question 2.
Sodium having atomic number 11, ready to ………….. electron/ electrons to attain the
nearest Noble gas electronic configuration.
(a) gain one
(b) gain two
(c) lose one
(d) lose two
Answer:
(c) lose one

Question 3.
The element that would form anion by gaining electrons in a chemical reaction is …………………
(a) Potassium
(b) Calcium
(c) Fluorine
(d) Iron
Answer:
(c) Fluorine

Question 4.
Bond formed between a metal and non metal atom is usually ……………..
(a) ionic bond
(b) covalent bond
(c) coordinate bond
Answer:
(a) ionic bond

Question 5.
…………….. compounds have high melting and boiling points
(a) Covalent
(b) Coordinate
(c) Ionic
Answer:
(c) Ionic

Question 6.
Covalent bond is formed by …………………
Answer:
(a) transfer of electrons
(b) sharing of electrons
(c) sharing a pair of electrons
Answer:
(b) sharing of electrons

Question 7.
Oxidising agents are also called as …………….. because they remove electrons from other
substances.
(a) electron donors
(b) electron acceptors
Answer:
(b) electron acceptors

Question 8.
Elements with stable electronic configurations have eight electrons in their valence shell.
They are ………………..
(a) halogens
(b) metals
(c) noble gases
(d) non metals
Answer:
(c) noble gases

II. Answer in brief.

Question 1.
How do atoms attain Noble gas electronic configuration?
Answer:
Atoms can combine either by transfer of valence electrons from one atom to another or by sharing of valence electrons in order to achieve the stable noble gas electronic configuration.

Question 2.
NaCl is insoluble in carbon tetrachloride but soluble in water. Give reason.
Answer:
NaCl is an ionic compound that is soluble in polar solvents like water and insoluble in non-polar solvents like benzene (C₆H₆), carbon tetra chloride (CCl₄). Whereas, CCl₄ is an organic compound, hence it is insoluble m water

Question 3.
Explain Octet rule with an example.
Answer:
The tendency of atoms to have eight electrons in the valence shell is known as the ‘Octet rule’ or the ‘Rule of eight’.
Example: Sodium with atomic number 11 will readily loose one electron to attain Neon’s stable electronic configuration.

Question 4.
Write a note on different types of bonds.
Answer:
All the elements differ with each other in their valence shell electronic configuration. So the way in which they combine to form compounds also differs. Hence, there are different types of chemical bonding possible between atoms which make the molecules. Depending on the type of bond they show different characteristics or properties. Such types of bonding that are considered to exist in molecules are categorized as the Ionic bond, Covalent bond and Coordinate bond.

Question 5.
Correct the wrong statements.

1. Ionic compounds dissolve in non-polar solvents
2. Covalent compounds conduct electricity in molten or solution state

Answer:

1. Ionic compounds are soluble in polar solvents like water. They are insoluble in non-polar solvents like benzene (C₆H₆), carbon tetrachloride (CCl₄).
2. Ionic compounds conduct electricity in molten or solution state.Covalent compounds are non-conductors of electricity.

Question 6.
Complete the table given below.

Element	Atomic number	Electron distribution	Valence electrons	Lewis dot structure
Lithium	3
Boron	5
Oxygen	8

Answer:

Question 7.
Draw the electron distribution diagram for the formation of Carbon dioxide (CO₂) molecule
Answer:

Question 8.
Fill in the following table according to the type of bonds formed in the given molecule CaCl₂, H₂O, CaO, CO, KBr, HCl, CCl₄, HF, C0₂, Al₂Cl₆
Answer:

Ionic bond	Covalent bond	Coordinate covalent bond
CaO	H2O, HF	CO
CaCl2	CO2
KBr	CCl4, Al2Cl6

Question 9.
Choose the correct answer from the choices given below.
The property which is characteristics of an Ionic compound is that

1. it often exists as a gas at room temperature
2. it is hard and brittle
3. it undergoes molecular reactions
4. it has low melting point
5. it is hard and brittle

Answer:
2. it is hard and brittle

Question 10.
Identify the following reactions as oxidation or reduction

1. Na ➝ Na+ + e^–
2. Fe³⁺ + 2 e^– ➝ Fe⁺

Answer:
1. It is an Oxidation reaction.
Oxidation: A chemical reaction which involves the addition of oxygen or removal of hydrogen or loss of electrons is called oxidation.

2. It is a Reduction reaction.
Reduction: A chemical reaction which involves the addition of hydrogen or removal of oxygen or gain of electrons is called reduction.

Question 11.
Identify the compounds as Ionic/Covalent/Coordinate based on the given characteristics.

1. Soluble in non-polar solvents
2. undergoes faster/instantaneous reactions
3. Non-conductors of electricity
4. Solids at room temperature

Answer:

1. Covalent compounds
2. Ionic compounds
3. Covalent compounds
4. Ionic compounds

Question 12.
An atom X with atomic number 20 combines with atom Y with atomic number 8. Draw the dot structure for the formation of the molecule XY.
Answer:
Atom X is Calcium with atomic number 20 and atom Y is Oxygen with atomic number 8.

Question 13.
Considering MgCl₂ as ionic compound and CH₄ as a covalent compound give any two differences between these two compounds.
Answer:

MgCl2	CH4
Ionic compounds are crystalline solids at room temperature	It occurs in gaseous state
It has high melting and boiling point	Have relatively low melting point
Soluble in polar solvents and insoluble in non-polar solvent	Soluble in non-polar solvents and insoluble in polar solvents

Question 14.
Why are Noble gases inert in nature?
Answer:
Noble gases have a stable valence electronic configuration. So noble gas atoms neither have any tendency to gain nor lose electrons and their valency is zero. Thus they are said to be inert.

III. Answer in detail.

Question 1.
List down the differences between Ionic and Covalent compounds.
Answer:

Ionic Compound	Covalent Compound
Ionic compounds are crystalline solids at room temperature	It occurs in gaseous state
They are poor conductors of electricity in solid state. However, in molten state and their aqueous solutions conduct electricity.	They are bad conductors of electricity
It has high melting and boiling point	Have relatively low melting point
Soluble in polar solvents and insoluble in non-polar solvent	Soluble in non-polar solvents and insoluble in polar solvents
They have high density and they are quite hard because of the strong electrostatic force between the ions. But they are highly brittle	They are neither hard nor brittle. But they are soft and waxy
Undergoes ionic reactions which are practically rapid and instantaneous	Undergo molecular reactions in solutions and these reactions are slow

Question 2.
Give an example for each of the following statements.
a. a compound in which two Covalent bonds are formed
b. a compound in which one ionic bond is formed
c. a compound in which two Covalent and one Coordinate bonds are formed
d. a compound in which three covalent bonds are formed
e. a compound in which Coordinate bond is formed
Answer:
a. Formation of oxygen molecule (O₂)
Each oxygen atom has six valence electrons (2, 6). These two atoms achieve a stable electronic configuration (octet) by sharing two pair of electrons. Hence a double bond is formed in between the two atoms.

b. Formation of Magnesium Chloride (MgCl₂)
Magnesium Chloride (MgCl₂) is an ionic compound formed when the magnesium ion loses two electrons to gain the noble state which is accepted by chloride ion.

c. Formation of coordinate covalent bond between NH₃ ➝ BF₃ molecules
Answer:
NH₃ ➝ BF₃ is a compound formed by coordinate covalent bonding. Here one pair of electrons from ammonia molecule is shared with electron deficit boron trifluoride. This type of bonding is also known as Dative bond.

d. Formation of nitrogen molecule (N₂)
Nitrogen molecule (N₂) is formed by three covalent bonds where three pairs of electrons are shared between the two to achieve a stable configuration.

e. Formation of coordinate covalent bond in ammonium ion (NH₄₊)
In ammonia molecule the central nitrogen atom has five valence electrons (2,5) among which three electrons are shared with three hydrogen atoms and still it has an unshared lone pair of electrons. This lone pair electron are donated to a Hydrogen ion and thus a N ➝ H coordinate covalent bond is formed in ammonium ion-molecule (NH₄₊).

Question 3.
Identify the incorrect statement and correct them.

1. Like covalent compounds, Coordinate compounds also contain charged particles (ions), so they are good conductors of electricity
2. Ionic bond is a weak bond when compared to Hydrogen bond.
3. Ionic or electrovalent bonds are formed by mutual sharing of electrons between atoms.
4. Loss of electrons is called Oxidation and Gain of electron is called Reduction.
5. The electrons which are not involved in bonding are called valence electrons.

Answer:

1. Like covalent compounds, coordinate compounds also do not contain charged particles (ions), so they are bad conductors of electricity
2. An ionic bond is formed by the electrostatic attraction between positive and negative ions. Hence it is stronger than Hydrogen bonding which is formed by electronegativity.
3. The ionic bond is formed between two atoms when one or more electrons are transferred from the valence shell of one atom to the valence shell of the other atom. The atom that loses electrons will form a cation (positive ion) and the atom that gains electrons will form an anion (negative ion).
4. Loss of electrons is called Oxidation and Gain of electrons is called Reduction.
5. The electrons which are involved in bonding are called valence electrons.

Question 4.
Discuss in brief the properties of Coordinate covalent compounds.
Answer:
The compounds containing coordinate covalent bonds are called coordinate covalent compounds.

1. Physical state – These compounds exist as gases, liquids or solids.
2. Electrical conductivity – Like covalent compounds, coordinate compounds also do not contain charged particles (ions), so they are bad conductors of electricity.
3. Melting point – These compounds have to melt and boiling points higher than those of purely covalent compounds but lower than those of purely Ionic compounds.
4. Solubility – Insoluble in polar solvents like water but are soluble in non-polar solvents like benzene, CCl₄, and toluene.
5. Reactions – Coordinate covalent compounds undergo molecular reactions which are
   slow.

Question 5.
Find the oxidation number of the elements in the following compounds,

1. C in CO₂
2. Mn in MnSO₄
3. N in HNO₃

Answer:

1. Oxidation number of C in CO₂ is +4
2. Oxidation number of Mn in MnSO₄ is +2
3. Oxidation number of N in HNO₃ is +5

Samacheer Kalvi 9th Science Chemical Bonding In-Text Problems

Question 1.
Find the oxidation number of Mn in KMnO₄
Solution:
+ 7.
Since the manganese atom is attached to four oxygen atoms through three double bonds and one single bond.

Question 2.
Find the oxidation number of Cr in Na₂Cr₂O₇.
Solution:
+ 6.

Question 3.
Find the oxidation number of Cu in CuS04.
Solution:
+ 2

Question 4.
Find the oxidation number of Fe in FeO.
Solution:
+ 2

Samacheer Kalvi 9th Science Chemical Bonding Additional Questions

I. Short answers questions.

Question 1.
What is an ionic or electrovalent bond?
Answer:
The oppositely charged ions are held together by electrostatic force of attraction which is called Ionic or Electrovalent bond.

Question 2.
What is electrovalency?
Answer:
The number of electrons that an atom of an element loses or gains to form an electrovalent bond is called electrovalency.

Question 3.
Write a short note on oxidizing and reducing agents.

1. Substances that have the ability to oxidize other substances are called oxidizing agents. These are also known as electron acceptors as they remove electrons from other substances. Example H202, Mn04, Cr03, Cr20?
2. The substances that have the ability to reduce other substances are called reducing agents. These are also called as electron donors as they donate electrons to other substances. Example – NaBEl₄, LiAlH₂ and metals like palladium and platinum

Question 4.
What is a redox reaction?
Answer:
Generally, the oxidation and reduction occurs in the same reaction (simultaneously). If one reactant gets oxidised, the other gets reduced. Such reactions are called oxidation-reduction ‘ reactions or Redox reactions.
Ex: 2 PbO + C ➝ 2Pb + C0₂

II. Long answers questions.

Question 1.
Mention some oxidation reactions that occur in daily life.
Answer:
In nature the oxygen present in atmospheric air oxidises many things, starting from metals to living tissues.

• The shining surface of metals tarnishes due to the formation of respective metal oxides on their surfaces. This is called corrosion.
• The freshly cut surfaces of vegetables and fruits turns brown after some time because of the oxidation of organic compounds present in them.
• The oxidation reaction in food materials that were left open for a long period is responsible for spoiling of food. This is called Rancidity.

Question 2.
What is Fajan’s rule? Discuss.
Answer:
As we know, a metal combine with a nonmetal through ionic bond. The compounds so formed are called ionic compounds. A compound is said to be ionic when the charge of the cation and anion are completely separated. But in 1923, Kazimierz Fajans found, through his X-Ray Crystallographic studies, that some of the ionic compounds show covalent character. Based on this, he formulated a set rules to predict whether a chemical bond is ionic or covalent. Fajan’s rules are formulated by considering the charge of the cation and the relative size of the cation and anion.

• When the size of the cation is small and that of anion is large, the bond is of more covalent character.
• Greater the charge of the cation, greater will be the covalent character.

Question 3.
What are the differences between ionic, covalent and coordinate covalent bond?
Answer:

Ionic Compound	Covalent Compound	Coordinate covalent bond
Ionic compounds are crystalline solids at room temperature	It occurs in gaseous state	It can exist as gases, liquids or solids
They are poor conductors of electricity in solid state. However, in molten state and their aqueous solutions conduct electricity.	They are bad conductors of electricity	Coordinate compounds also do not contain charged particles (ions), so they are bad conductors of electricity
It has high melting and boiling point	Have relatively low melting point	Have melting and boiling points higher than that of purely covalent compounds but lower than those of purely Ionic compounds
Soluble in polar solvents and insoluble in non-polar solvent	Soluble in non-polar solvents and insoluble in polar solvents	Soluble in non-polar solvents and insoluble in polar solvents
They have high density and they are quite hard because of the strong electrostatic force between the ions. But they are highly brittle	They are neither hard nor brittle. But they are soft and waxy
Undergoes ionic reactions which are practically rapid and instantaneous	Undergo molecular reactions in solutions and these reactions are slow	Undergoes slow molecular reactions which are slow.

You can Download Samacheer Kalvi 9th English Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

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Tamilnadu Samacheer Kalvi 9th English Article Writing

An article is a piece of written work, the purpose of which is to propagate news, inform about results of research, analyze academic information, express opinions or persuade through suggestions.

Components of an article :
Title – it should be catchy enough to draw the reader’s attention
Byline – the name of the writer of the article Introduction – outlines the topic
Body – builds upon the topic; consists of two to four paragraphs
Conclusion – summarises and offers final opinions

Tips for writing articles :

• Be brief and concise.
• Cover the essential elements of who, what, when, where, how and why?
• Focus on the theme or topic of the article. Do not deviate from it.
• Use simple language.

Exercises
1. Write an article for your school magazine. Describing your experience about the Clean India Campaign.
Answer:

Clean India Campaign

– by Anitha

The ‘Clean India Campaign’ or ‘Swachh Bharat Abhiyan’ launched by our Prime Minister, Mr. Narendra Modi was implemented to fulfill the vision of a clean India. But it has not been as effective as it should have been opinion polls conducted in various cities of India suggested that nearly two-thirds of the residents surveyed felt there was no impact of the campaign on their city or surroundings. The fact remains that the government alone cannot bring about a change unless we the people take initiatives to keep our surroundings clean. It is all about changing our attitude which cannot be changed by imposing fines of punishments.

There is a significant percentage of our population who are totally unaware of and neglect basic cleanliness hygiene. These are people who don’t even think once before littering on the road or throwing garbage anywhere and everywhere. Their lack of awareness has led to the ineffectiveness of such cleanliness initiatives. It is important to sensitize people on the importance of hygiene and cleanliness through awareness programs in electronic, print and social media. Enlightened people need to work with not only individuals but also organizations to make those people aware of the importance of cleanliness.

2. Write an article for your school magazine. Describing your experience about River Pollution.
Answer:

River Pollution

– by Rama

It is indeed unfortunate that rivers, which are our largest source of water are victims of pollution. Countless tanneries, chemical plants, textile mills, slaughter houses, hospitals contribute to pollution of rivers by dumping untreated waste into it. People who do not have the proper living conditions in India, resort to carrying out all their daily activities like bathing, washing and defecation, on the bank of rivers, and thus pollute them. Discharge of sewage and other domestic waste into the rivers is yet another environmentally hazardous practice, that is polluting the rivers. Religious practices also demand that floral offerings be cast-off in rivers and the ashes, after cremating a person should also be poured into rivers.
Unfortunately one concludes despite laws dealing with the task of prevention and control of river pollution there is no end to the misery we humans inflict on our rivers.

3. Write an article for your school magazine. Describing your experience about Serve Mankind.
Answer:

Serve Mankind

– by Bala

Men represent society in a Microform. God made man to serve those who need the service. It may be in any field or in any form. But the best form is “Voluntary Community Work” which means that the work should be done not for an individual but for all. For example, I see that the village is full of garbage. Let us together dig pits far away from the village and bury these garbage there, which will turn to manure in a couple of years’ time.

At the same time, the removal of the garbage will give a better look to the village. The second community work for our village is to make drains. Let us control the dirty water and direct it to the pits where the garbage has been buried. But this is not the work done by one or two men. Let the people realise that the best service to God is to serve His creation.

4. Write an article for your school magazine. Describing your experience about school picnic.
Answer:

SCHOOL PICNIC TO MAMALLAPURAM

– by Srinivasan

School picnics are the most awaited ones. They are with great fun. The memories of school picnics are the one to be cherished for a lifetime. This year’s picnic was destined to be at Mamallapuram which is situated around 60 km from Chennai. On the day of the picnic, we reported to the school assembly hall at 5 a.m. Since it was the last week of December, the weather was very cold. The school bus departed at sharp 5.10 a.m. in the morning. Almost one and half hour travel to the heritage town felt like a matter of few minutes. We reported to the guest house at around 6.30 a.m., we were all provided welcome drinks. Then we left for the Shore Temple.

Sunrise at Shore Temple is an unforgettable sight. Five Rathas, Cave Temple, Tiger Cave, Elephant and other creatures carved in granite, Arjuna’s Penance, Lord Krishna’s Butter Ball (a huge stone almost spherical in shape) are the important sculptures to be seen there. It was the most exciting part of the picnic. Then we had lunch, followed by some fun activities. The time had passed so soon that we couldn’t even realize the day was over. This was indeed a day I will remember for a long time.

You can Download Samacheer Kalvi 9th English Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

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Tamilnadu Samacheer Kalvi 9th English Speech Writing (on a given

topic)

Exercises
1. How do you prepare a speech for the morning assembly, stressing on the importance of ‘Sound mind in a sound body?
Answer:

Sound Mind In A Sound Body

Respected teachers and students,
Warm greetings to all of you.
I am here to deliver a speech on “Sound mind in a sound body”.

‘A sound mind in a sound body’ is the adage. It is true and worthy. The mind when free from pain or physical stress thinks clearly and remains active. It has the ability to march towards its goal as there are no stress psychologically and physically due to fear and illness. Active exercises, fresh air, activities like cycling, swimming and walking refresh the mind and keep it cheerful and relaxed. To overcome our stress we should play our favorite game, be it chess, cricket or any other game and remain calm and relaxed. Hence sports are an essential part of life.

Thank you for listening to my speech.

2. Prepare a speech in about 80-100 words of the morning assembly on highlighting the importance of Saving Water.
Answer:

Saving Water

Water is used by us for various purposes. Water is used for drinking. The human body depends on water for survival. Water is used for cooking food too. The water that we need for consuming must be clean, potable water. If humans use dirty or contaminated water for these purposes they can fall sick and die from the diseases. Therefore, for good health we need clean drinking water to be available for our use. Water is also needed for farming. We also use water to maintain personal hygiene. We also need water to wash our clothes, as also to keep our homes and surroundings clean.

3. Prepare a speech in about 80-100 words of the morning assembly on highlighting the importance conservation of Nature.
Answer:

Conservation Of Nature

Nature fulfills our basic requirement to live by providing us air, water, land, sunlight and plants. These resources are further used to manufacture various things that make life more convenient and comfortable for human beings. As a result, many of these resources are depleting at a fast pace and if it continues this way then the survival of human beings, as well as other living beings on Earth, would become very difficult. Conservation of nature means the preservation of forests, land, water bodies and conservation of resources such as minerals, fuels, natural gases, etc. to ensure that all these continue to be available in abundance.

4. Prepare a speech in about 80 – 100 words of the morning assembly on highlighting the importance of Saving Trees.
Answer:

Saving Trees

Respected teachers and students,
Warm greetings to all of you.
I am here to deliver a speech on “Saving Trees”.

Trees play a significant role in our daily life. Trees provide oxygen. They absorb carbon dioxide, thereby reducing the global warming. They provide food for us and also for forest animals. Trees offer habitation to birds, insects, lichen and fungi. Their trunks provide the hollow cover needed by species such as bats, wood-boring beetles, owls and woodpeckers. They benefit the environment by the way of preventing soil erosion and flooding. They reduce the speed of the wind. They act as natural air conditioners by cooling the roadsides by their shade. They are helpful for children to play in and discover their sense of adventure. They also help in protecting us from the harmful effect of ultra-violet rays. So it is our responsibility to save trees.

Thank you for listening to my speech.

5. Prepare a speech in about 80-100 words on Peacock.
Answer:

Peacock

Peacock is one of the most beautiful birds on the earth. It is particularly known for its colourful feathers that are a sight to behold. It looks best when it dances merrily in » the rain. Peacock is the national bird of India. It finds several references in the Indian mythology and history. It is known for its metallic blue and green colour and spectacular feather. These feathers are also considered auspicious and are used to bring in good luck and prosperity. Peacock has inspired many notable artists in the past and continues to do so.

6. Prepare a speech in about 80-100 words of the morning assembly on highlighting the Importance of Saving Pets.
Answer:

Saving Pets

Respected teachers and students,
Warm greetings to all of you.
I am, here to deliver a speech on “Saving Pets”.

Saving the life of a pet animal like a dog or a cat is our moral responsibility. There are so many ways in which we can save pets. A person can adopt his pet and encourage his friends and family to adopt pet. Most people don’t realize that they are unknowingly supporting the puppy mill industry when they purchase animals from pet stores or buy a puppy online. A person may talk with the owners of pet stores and ask them to feature homeless pets for adoption instead. We can add an advocacy message in the signature line of our email to help educate people about the issue.

Instead of buying pet animals, we can adopt them. We can use our social networking skills to promote adoptable animals. Most rescue groups need volunteers who can help with a variety of professional services. So as a volunteer, we can save a lot of lives. There are lots of ways to provide assistance without giving a donation. However, donations allow shelters and rescue groups to increase adoptions, promote spay/neuter, create lifesaving programs, educate the public about animal welfare issues, and much more. A person can save lives by fostering homeless animals.

Thank you for listening to my speech.

You can Download Samacheer Kalvi 9th English Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

Exploring the textbook concepts is not enough for students who dreamt to do a cakewalk in English grammar. Consistently do your learning and practicing session with Samacheer Kalvi 9th English Grammar study material and achieve all your dreams.

Tamilnadu Samacheer Kalvi 9th English Letter Writing (to a friend)

Various parts of a formal letter

1. the heading
2. the inside address
3. the salutation
4. the body
5. the closing
6. the signature
7. the address on the envelope

The contents of a formal letter

• Use a courteous, positive and professional tone. Maintain a respectful, constructive tone.
• Use formal language. Avoid contractions or abbreviations.
• State your purpose clearly and briefly. State the purpose of your writing in the first or second sentence of the letter.
• Include all necessary information. Provide all the information your reader needs to understand and respond appropriately to your letter.

Format for Business and Official Letters:
Business : to dealers for buying and selling goods or comments on goods purchased.
Official : to Officials, to Principals, Teachers.

(a) Station (Place): y city
(b) Date: e.g. 20th Jan. 2019
(c) From Address
(d) To Address
(e) Salutation:
Sir, Dear Sir, Respected Sir, Madam (Principal, Teacher)
(f) Sub:
(i) Complaint on
(ii) Requisition for.
(iii) Orders placed on
(iv) Reminder on
(g) Ref:

Complaint letter
Bill No. _______ dated _______ (Reminder letter)
Previous letter dated
(h) Commencing lines :
(a) This is to inform you that
(b) I wish to bring to your kind notice that …………………………
(i) Content of the letter :
(j) Request:
(a) I shall be very grateful if the necessary measures are taken by the authorities concerned at the earliest
(b) I shall be obliged if early measures are taken in this regard by the authorities concerned
(k) Thank you,
(l) Subscription:
Yours truly,
Yours faithfully,
(m) Signature:
x x

Format For Personal Letter:

(a) From Address :
Y City

(b) Date : Eg. 20th June, 2019
(c) Salutation:
My Dearest __, Dearest __, Dear __,

(d) Commencing Lines:

1. Hope this letter finds you in the best of health
2. Hope you had received my previous letter
3. Thank you for your loving letter
4. Happy to meet you through this letter
5. Thank you for the you had sent me

(e) Concluding Lines:

1. Looking forward to your reply
2. Awaiting your reply / coming eagerly
3. Convey my love/regards to

(f) Subscription:
For Parents, Uncles,
Aunts – Yours lovingly,
For Friends – Yours lovingly, sincerely,
For Brother, Sisters, Cousins,
nephews, nieces – Yours affectionately,

(g) Signature

Exercises
1. Kumar wants to invite his friend Siva for his sister’s Marriage a week earlier, to assist him in the arrangments. He could not complete the content of his letter in about 100 words.
Answer:
Chennai,
23rd January 2019.

My Dear Siva,
Hope this letter finds you in good health. It’s been a few months since we’ve met. I have a good news. My sister, Shanthi’s marriage has been fixed on 30th of this month. We would like to have your presence two days ahead. So please be part of the family. Looking forward to be with you. We need your ideas for the reception hall and its decoration. All of us are expecting your arrival soon.

Your loving friend,
Kumar

Address on the envelope :
To
Mr. S. Siva,
20, Anna Salai,
Salem.

2. Kavya wanted to write a letter to her uncle to ask him if she could spend her summer holidays with him. She had started her letter but had not completed it. Complete the content of her letter in about 100 words.
Answer:
No. 20,4th Street,
Gandhi Nagar,
Chennai – 600 020.
13 th December, 2018.

Dear Uncle,
Hope this letter finds you in the best of health. Uncle, with my exams over and with the long wait for the results, I thought I could spend my summer holidays with you, aunt and brothers Ramu and Raju in the fields and plantation in the village.

It would be very refreshing after my exam and I am looking forward to put my hands to work. Shall I be there on Sunday? My father will drop me at the village.

Waiting for your reply or phone call at the earliest.

Your loving
niece,

Address on the envelope :

To
Mr. Vasanth,
20, Everon Heights, Ootacamund,
Nilgiris District.

3. Write a letter to your friend telling about how your house was burgled when your family was away on a holiday. (*^)
Answer:
36, Gandhi Road
Chennai – 45
04 August 2018

Dear Ramesh,
How are you? I feel sad to inform you that my house was burgled last week when I was on a holiday. Burglars might have known from the accumulated newspaper pile that I had gone away. When I came back last Sunday, I found the back-door lock broken. I could have forgotten to bolt the back-door from inside and they should have entered through it. My room was ransacked. They took my laptop and other valuables. I must have deposited the jewellery in a bank locker to avoid this loss. I should have informed my neighbours about my week-long trip. Well, I have registered an FIR with the police. They are investigating the case. They have assured that I would get my jewels back. The burglars will be caught very soon. Convey my regards to all at home.

Yours lovingly,
Murali

Address on the envelope :
Mr. Ramesh,
50, Bharathiyar Street,
Namakkal.

4. Suba wanted to write a letter to her friend congratulating her for her victory in Para Olympic Games. She had the format ready but Is yet to complete the letter. Complete the content of her letter in about 100 words.
Answer :
9/11, Kinely Street,
R City
2nd February, 2019.

Dear Rajalakshmi,
I am fine. How are you? I am very delighted to know that you have got victory in Para Olympic Games. Please accept my heartiest congratulations for this great achievement. Actually, your selfless dedication and devotion to the cause pf Sports and Games have earned you this deserving recognition. This is just the beginning and many such victories and medals should follow.

Your loving friend,
sudha

Address on the envelope :
To
Miss Rajalakshmi,
27, Woodland Street,
Ooty.

You can Download Samacheer Kalvi 9th Science Book Solutions Guide Pdf, Tamilnadu State Board help you to revise the complete Syllabus and score more marks in your examinations.

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 12 Periodic Classification of Elements

Samacheer Kalvi 9th Science Periodic Classification of Elements Textbook Exercises

I. Choose the correct answer.

Question 1.
If Dobereiner is related with ‘law of triads’, then Newlands is related with ……………………
(a) Modern periodic law
(b) Hund’s rule
(c) Law of octaves
(d) Pauli’s Exclusion principle
Answer:
(c) Law of octaves

Question 2.
Modem periodic law states that the physical and chemical properties of elements are the periodic functions of their ……………
(a) atomic numbers
(b) atomic masses
(c) similarities
(d) anomalies
Answer:
(a) atomic numbers

Question 3.
Elements in the modem periodic table are arranged in …………. groups and ………. periods.
(a) 7, 18
(b) 18, 7
(c) 17, 8
(d) 8, 17
Answer:
(b) 18, 7

II. Fill in the blanks.

1. In Dobereiner’s triads, the atomic weight of the middle element is the ……………….. of the atomic masses of 1st and 3rd elements.
2. Noble gases belong to ……………….. group of the periodic table.
3. The basis of the classifications proposed by Dobereiner, Newlands, and Mendeleev was…………………..
4. An example of liquid metal is …………………..

Answer:

1. average
2. 18th
3. atomic masses
4. Mercury

III. Match the following.

Column – I	Column – II
1. Triads	(a) Newlands
2. Alkali metal	(b) Calcium
3. Law of octaves	(c) Henry Moseley
4. Alkali earth metal	(d) Sodium
5. Modem Periodic Law	(e) Dobereiner

Answer:

1. (e) Dobereiner
2. (d) Sodium
3. (a) Newlands
4. (b) Calcium
5. (c) Henry Moseley

IV. State whether True or False.

1. Newlands’ periodic table is based on atomic masses of elements and modem periodic table is based on the atomic number of elements – True
2. Metals can gain electrons – False.
   Correct Statement: Metals tend to lose electrons to attain Noble Gas electron configuration.
3. Alloys bear the characteristics of both metals and nonmetals – False
   Correct Statement: An alloy is a mixture of metals or a mixture of a metal and another element.
4. Lanthanides and actinides are kept at the bottom of the periodic table because they resemble each other but they do not resemble any other group elements – True
5. Group 17 elements are named as Halogens – True

V. Assertion and Reason

Statement: Elements in a group generally possess similar properties but elements along a period have different properties.
Reason: The difference in electronic configuration makes the element differ in their chemical properties along a period.
(a) Statement is true and the reason explains the statement.
(b) Statement is false but the reason is correct.
Answer:
(a) Statement is true and reason explains the statement.

VI. Answer the following.

Question 1.
State modern periodic law.
Answer:
“The Chemical and Physical properties of elements are periodic functions of their atomic number”.

Question 2.
What are groups and periods in the modern periodic table?
Answer:

• The horizontal rows are called periods. There are seven periods in the periodic table.
• Vertical columns in the periodic table starting from top to bottom are called groups. There are 18 groups in the periodic table.

Question 3.
What are the limitations of Mendeleev’s periodic table?
Limitations of Mendeleev’s periodic table:
Answer:

• Elements with large difference in properties were included in the same group. Eg: Hard metals like copper (Cu) and silver (Ag) were included along with soft metals like sodium (Na) and potassium (K).
• No proper position could be given to the element hydrogen. Non-metallic hydrogen was placed along with metals like lithium (Li), sodium (Na) and potassium (K).
• The increasing order of atomic mass was not strictly followed throughout. Eg. Co & Ni, Te & I.
• No place for isotopes in the periodic table.

Question 4.
State any five features of modern periodic table.
Answer:

• All the elements are arranged in the increasing order of their atomic number
• The horizontal rows are called periods. There are seven periods in the periodic table.
• The elements are placed in periods based on the number of shells in their atoms
• Vertical columns in the periodic table starting from top to bottom are called groups. There are 18 groups in the periodic table
• Based on the physical and chemical properties of elements, they are grouped into various families.

Activity

Question 1.
Find the pair of elements having similar properties by applying Newlands law of Octaves (Example: Mg & Ca):
Set I: F, Mg, C, O, B
Set II: Al, Si, S, Cl, Ca
Answer:

Set I:	F	Mg	C	0	B
Set II:	Cl	Ca	Si	s	Al

Samacheer Kalvi 9th Science Periodic Classification of Elements Additional Questions

I. Short answers questions.

Question 1.
Why did the classification of elements evolve?
Answer:
Scientists found it difficult to organize all that was known about the elements. Therefore they started looking for some pattern in their properties, and the concepts of classification of elements were proposed by various scientists. This led to the evolution of the classification of elements from the early to modem period.

Question 2.
What is a triads group?
Answer:
Johann Wolfgang Dobereiner arranged the elements into groups containing three elements each based on their relative, atomic masses. He called these groups as ‘triads’ also known as Dobereiner’s Triads.

Question 3.
Explain law of octaves.
Answer:
John Newlands arranged 56 known elements in the increasing order of their atomic mass. He observed that every eighth element had properties similar to those of the first element like the eighth note in an octave of music is similar to the first and this arrangement was known as “law’ of octaves”.

Question 4.
What is a periodic table?
Answer:
Dmitri Mendeleev proposed the law of periodicity which states that “the physical and chemical properties of elements are the periodic functions of their atomic masses”. He arranged 56 elements known at that time according to his law of periodicity. This was best known as the short form of the periodic table.

Question 5.
What is IUPAC? Where is it located? Give examples of few elements named by IUPAC.
Answer:
IUPAC stands for-The International Union of Pure and Applied Chemistry. It is an international organization that represents Chemists from various countries. IUPAC is registered in Zurich, Switzerland and has its secretariat in the United States.

Question 6.
How are metals classified in the periodic table?
Answer:
Metals occupy a larger area in the periodic table and are categorized as follows –

• Alkali metals eg. – Sodium and Potassium
• Alkaline earth metals eg. – Calcium and Magnesium
• Transition metals eg. – Iron and Nickel
• Other metals eg. – Aluminium and Tin

Question 7.
What are alkali metals?
Answer:
The elements of group 1 (except hydrogen) are metals. They react with water to form solutions that are highly alkaline or basic. Hence they are called alkali metals.

Question 8.
Though they are found rare, they have many uses. Justify this statement.
Answer:
Helium, Neon, Argon, Krypton, Xenon, and Radon are called the Noble or rare gases and are placed in group 18 in the periodic table. They are monoatomic and do not react with other substances easily. Though these gases are chemically inert, they have stable electronic structures which are difficult to change. Their uses are as follows:

1. Helium has a very low density and used for filling weather ballon.
2. Neon gas is used in discharge lamps.
3. Argon is filled in electrical bulbs to prevent evaporation of the filament.
4. Radon is a radioactive gas.

II. Long Answers Questions.

Question 1.
Write any five advantages of the modern periodic law.
Answer:

• The table is based on a more fundamental property i.e., atomic number.
• It correlates the position of the element with its electronic configuration more clearly.
• The completion of each period is more logical. In a period, as the atomic number increases, the energy shells are gradually filled up until an inert gas configuration is reached.
• Each group is an independent group and the idea of subgroups has been discarded.
• One position for all isotopes of an element is justified since the isotopes have the same atomic number.

Question 2.
Explain the limitations of Mendelev’s periodic table and why is the modern periodic table considered an extension of Mendeleev’s periodic table.
Limitations of Mendelev’s periodic table –
(a) Elements with large difference in properties were included in the same group. Eg. Elard metals like copper (Cu) and silver (Ag) were included along with soft metals like sodium and potassium
(b) No proper position could be given to the element hydrogen. Non-metallic Hydrogen was placed along with metals like lithium, sodium and potassium.
(c) The increasing order of atomic mass was not strictly followed throughout. Eg. – Co & Ni, te & I.
(d) No place for isotopes in the periodic table.

The modem periodic table is an extension of the original Mendeleev’s periodic table and is known as the long form of periodic table. Mendeleev’s initial table had 63 elements, modem table has 109 elements. It is also known important to note how the modem periodic table is arranged.

Although the columns which reflect a natural order have been retained, the row’s of the modem table show elements in the order of Mendeleev’s columns. In other words the elements of what we now call ‘a period’ were listed vertically by Mendeleev. ‘Groups are now shown vertically in contrast to their horizontal format in Mendeleev’s table.

Question 3.
What are the advantages of alloys?

• Alloys do not get corroded or get corroded to very less extent.
• They are harder and stronger than pure metals (example: gold is mixed with copper and it is harder than pure gold).
• They have less conductance than pure metals (example: copper is good conductor of heat and electricity whereas brass and bronze are not good conductors).
• Some alloys have lower melting point than pure metals (example: solder is an alloy of lead and tin which has lower melting point than each of the metals).
• When metal is alloyed with mercury, it is called amalgam.

Question 4.
Explain the uniqueness of Hydrogen.
Answer:
Hydrogen is the lightest, smallest and first element of the periodic table. Its electronic configuration (Is1) is the simplest of all the elements. It occupies a unique position in the periodic table. It behaves like alkali metals as well as halogens in its properties. In the periodic table, it is placed at the top of the alkali metals.

1. Hydrogen can lose its only electron to form a hydrogen ion (H+) like alkali metals.
2. It can also gain one electron to form the hydride ion (H-) like halogens.
3. Alkali metals are solids while hydrogen is a gas.