Chapter Practice

Which of the following statements is not a correct

PART 1

statement about the trends when going from left to

right across the periods of periodic table?

(NCERT)

Objective Questions

(a) The elements become less metallic in nature

(b) The number of valence electrons increases

●

Multiple Choice Questions

(d) The oxides become more acidic

Dobereiner could identify how many triads from the

elements known at that time ?

10.

Match the following columns :

(a) One

(b) Two

(d) Four

Column I

Column II

Upto which element, the law of octaves was found to

(Elements)

(Groups)

be applicable?

(NCERT Exemplar)

A. Be

(i) Group 17

(a) Oxygen

(b) Calcium

(d) Potassium

B. F

(ii) Group 15

What type of oxide would Eka-aluminium form?

C. P

(iii) Group 2

(NCERT Exemplar)

D. Ar

(iv) Group 18

(a) EO₃

(b) E₃O

(d) EO

Codes

Which one of the following elements exhibit maximum

A B C D

(a)

(iii)

(i)

(ii)

(iv)

(b) (i)

(ii)

(iii) (iv)

number of valence electrons?

(NCERT Exemplar)

(c)

(ii)

(iv) (iii) (i)

(d) (iv)

(ii)

(i)

(iii)

(a) Na

(b) Al

(d) P

11.

Which metal is among the first ten elements in

Choose the correct statement.

modern periodic table?

(a) Valency and valence electrons are always equal

(a) Lithium (Li)

(b) Boron (B)

(b) Valency is determined by using the number of valence

(d) Potassium (K)

electrons

12.

An element X is forming an acidic oxide. Its position

(d) Valency is always equal to 8-valence electrons

in modern periodic table will be

(CBSE 2020)

(a) group 1 and period 3

(b) group 2 and period 3

Elements with code letters Q and R occupy the

(d) group 16 and period 3

positions shown in the outline of the periodic table.

13.

An oxide of a metal shows no action with blue-litmus

but turns red-litmus to blue in its aqueous solution.

The possible formula of the metal oxide can be

(a) MgO

(b) CO₂

(d) H O

What is the formula of the compound formed

14.

The position of four elements A, B, C and D in the

between them?

modern periodic table are shown below. The

(a) QR₂

(b) Q R

(d) Q R

element which is most likely to form a basic oxide is

Which of the following statements is incorrect for

atomic size ?

(a) Atomic size of B > Be

(b) Atomic size of Be > B

(d) Atomic size of C > N

Which of the following gives the correct increasing

order of the atomic radii of O, F and N?

(NCERT Exemplar)

(a) B

(b) C

(d) D

(a) O, F, N

(b) N, F, O

(d) F, O, N

15. Consider the part of periodic table given below:

Modern periodic law states that ‘‘the physical and

chemical properties of all the elements are the

Group/Period

periodic function of their atomic radius.

The atomic radii of group 1 and group 2 elements

b e

g h

are given in the table.

III

Group 1 Atomic radii (nm) Group 2 Atomic radii (nm)

0.152

0.112

The most electropositive element is

0.186

0.160

(a) c

(b) d

(d) k

0.231

0.197

^● Assertion-Reasoning MCQs

0.244

0.215

0.262

0.217

Direction (Q. Nos. 16-20) Each of these questions

contains two statements Assertion (A) and Reason (R).

0.270

0.220

Each of these questions also has four alternative choices,

(i) Who discovered modern periodic table?

any one of which is the correct answer. You have to select

(a) Henry Moseley

one of the codes (a), (b), (c) and (d) given below.

(b) Johann Wolfgang Dobereiner

(a) Both A and R are true and R is the correct explanation

of A.

(d) Dmitri Ivanovich Mendeleev

(b) Both A and R are true, but R is not the correct

explanation of A.

(ii) Along the period 3, which atom can loose electron

easily?

(d) A is false, but R is true.

(a) Li

(b) Na

(d) Mg

16.

Assertion Be, Mg and Ca can be classified as

(iii) Which metal has the highest metallic character in

Dobereiner’s triads.

group 1?

(a) Li

(b) Na

(d) Rb

Reason Atomic mass of Mg is approximately the

average of the sum of atomic masses of Be and Ca.

(iv) Which of the following properties increases down

the group?

17.

Assertion Sodium is an element of group 1 of the

(a) Electronegativity

modern periodic table.

(b) Electropositive nature of element

Reason All the elements of group 1 of the modern

periodic table contain two electrons in their

(d) Acidic oxide character

outermost shell.

(v) Which atom is most electronegative along the

18.

Assertion Noble gases are also called inert gases.

period 4?

Reason Noble gases have a complete octet.

(a) K

(b) Rb

(d) Ca

19.

Assertion Atomic size increases on going down the

22. Read the following and answer the questions from

group in the modern periodic table.

(i) to (v) given below

Reason New shells are being added as we go down

The noble gases make up a class of chemical

the group in the modern periodic table.

elements with similar properties under standard

conditions, they are all odourless, colourless,

20.

Assertion Electronegativity of flourine is greater than

monoatomic gases with very low chemical reactivity.

that of oxygen.

These gases are also called as inert gases or

Reason The electronegativity of the elements increases

aerogens. The properties of the noble gases can be

along a period since the metallic character increases.

well explained by modern theories of atomic

structure. Their outer shell of valence electrons is

^● Case Based MCQs

considered to be full, giving them little tendency to

21. Read the following and answer the questions from (i)

participate in chemical reactions.

to (v) given below

The linkage formed from one electrostatic attraction

The modern periodic table is based on the increasing

between oppositely charged ions in a chemical

order of atomic radius. The atomic size increases

compound is called ionic or electrocovalent bond.

down the group. This is because new shell are being

Such a bond forms when the valence electrons of

added as we go down the group. The atomic radius

one atom are transferred permanently to another

decreases in moving from left to right along a period.

atom.

The table given below refers to the elements of the

6. What were the criteria used by Mendeleev in

periodic table with atomic number from 3 to 18.

creating his periodic table?

(NCERT)

These elements are shown by letters.

7. In Mendeleev’s periodic table, the elements were

(Not by the usual symbols of the elements).

arranged in the increasing order of their atomic

masses. However, cobalt with atomic mass of

D E F G H

58.93 amu was placed before nickel having an

atomic mass of 58.71 amu. Give reason for the same.

(NCERT Exemplar)

M N O P

Write the formulae of chlorides of Eka-silicon

(i) Which of the following are noble gases ?

and Eka-aluminium, the elements predicted by

(a) H and P

(b) G and O

Mendeleev.

(d) A and I

9. Write two main characteristics of Mendeleev’s

(ii) Which are halogens ?

periodic table and write name of elements of second

(a) H and L

(b) C and M

period.

(d) E and P

10. How it can be proved that the basic structure of the

(iii) Which of the following elements have valency 4 ?

‘modern periodic table’ is based on the electronic

(a) F and N

(b) C and K

configuration of atoms of different elements?

(d) H and P

(CBSE 2019)

(iv) Which of the following can form ionic bond?

(a) B and H

(b) J and P

11. ‘Hydrogen occupies a unique position in modern

periodic table’. Justify the statement.(NCERT Exemplar)

(d) A and G

(v) Which of the following elements have 2 valence

12.

(i) List any two distinguishing features between

electrons?

Mendeleev’s periodic table and the modern

(a) D and L

(b) B and J

(d) C and K

periodic table.

(ii) With the help of an example, explain

Dobereiner’s Triads.

PART 2

(iii) State modern periodic law.

(CBSE 2020)

Subjective Questions

13. Write the formula of the product formed when the

element A (atomic number 19) combines with the

element B (atomic number 17). Draw its electronic

^● Short Answer Type Questions

dot structure. What is the nature of the bond

1. What were the limitations of Dobereiner’s

formed?

(NCERT Exemplar)

classification?

(NCERT)

14. Compare the radii of two species X and Y. Give

2. Can the following groups of elements be classified as

reasons for your answer.

Dobereiner’s triad?

(a) X has 12 protons and 12 electrons, (b) Y has 12

(i) Na, Si, Cl

(ii) Be, Mg, Ca

protons and 10 electrons

(NCERT Exemplar)

Atomic mass of Be-9; Na-23; Mg-24; Si-28; Cl-35; Ca-40

15. Arrange the following elements in increasing order of

Justify your answer in each case.

(CBSE 2019)

their atomic radii.

(i) Li, Be, F and N

(ii) Cl, At, Br and I

3. Did Dobereiner’s triads also exist in the columns of

(NCERT Exemplar)

Newlands’ octaves? Compare and find out.

(NCERT)

16. An element X of group 15 exists as diatomic

4. Elements have been arranged in the following

molecule and combines with hydrogen at 773 K in

sequence on the basis of their increasing atomic

presence of the catalyst to form a compound,

masses. F, Na, Mg, Al, Si, P, S, Cl, Ar, K.

ammonia which has a characteristic pungent smell.

(i) Pick two sets of elements which have similar

(i) Identify the element X. How many valence

properties.

electrons does it have?

(ii) The given sequence represents which law of

(ii) Draw the electron dot structure of the diatomic

classification of elements?

molecule of X. What type of bond is formed in it?

5. What were the limitations of Newlands’ law of

(iii) Draw the electron dot structure for ammonia and

octaves?

(NCERT)

what type of bond is formed in it?

17. A salt when dissolved in water dissociates

Answer the following question in relation to the

into cations and anions as follows:

above group of elements.

+H2O

(i) Which element has the most metallic character?

AB ! A+ + B⁻

(ii) Which element would be expected to have the

H2O

highest electronegativity?

If both the ions consist same number of electrons

(iii) Will the elements in the group to the right of this

and the molecular weight of salt is 74.5, then identify

boron group be more metallic or less metallic in

the position of A and B in the periodic table.

character? Justify your answer.

18. Three elements A, B and C have 3, 4 and 2 electrons

respectively in their outermost shell. Give the group

^● Long Answer Type Questions

number to which they belong in the modern periodic

24. Use Mendeleev’s periodic table to predict the

table. Also, give their valencies.

(NCERT Exemplar)

formulae for the oxides of the following elements.

19. Based on the group valency of elements, write the

K, C, Al, Si and Ba.

(NCERT)

molecular formula of the following compounds

25. Compare and constrast the arrangement of element in

giving justification for each.

Mendeleev’s periodic table and the modern periodic

(i) Oxide of first group elements

table.

(NCERT)

(ii) Halide of the elements of group thirteen

26. An element is placed in 2nd group and 3rd period of

(iii) Compound formed when an element A of group

the periodic table, burns in presence of oxygen to

2 combines with an element, B of group seventeen.

(CBSE 2019)

form a basic oxide.

(NCERT Exemplar)

(i) Identify the element.

20. From the elements Li, K, Mg, C, Al, S identify the

(i) elements belonging to the same group.

(CBSE 2020)

(ii) Write the electronic configuration.

(ii) element which has the tendency to lose two electrons.

(iii) Write a balanced equation when it burns in the

presence of air.

(iii) element which prefers sharing of electrons to

complete its octet.

(iv) Write a balanced equation when this oxide is

(iv) most metallic element.

dissolved in water.

(v) element that forms acidic oxide.

(v) Draw the electron dot structure for the formation of

(vi) element that belongs to group 13.

this oxide.

21. The following table shows the position of five

27. Which elements has

elements A, B, C, D and E in the modern periodic

(i) two shells, both of which are completely filled with

table.

electrons?

Group →

3 to 12

(ii) the electronic configuration 2, 8, 2?

Period ↓

(iii) a total of three shells, with four electrons in its

valence shell?

(iv) a total of two shells, with three electrons in its

valence shell?

Answer the following giving reasons:

(v) twice as many electrons in its second shell as in its

(i) Which element is a metal with valency two?

first shell?

(NCERT)

(ii) Which element is least reactive?

(iii) Out of D and E which element has a smaller atomic

28. An element X (atomic number = 17 ) reacts with an

radius?

(CBSE Sample Paper)

element Y (atomic number = 20) to form a divalent

halide.

22.

(i) What term can be used for the elements separating

(i) Where in the periodic table are elements X and Y

metal from non-metals and why?

placed?

(ii) Give the names of the metalloids in the periodic

(ii) Classify X and Y as metal(s), non-metal(s) or

table along with their atomic number.

metalloid(s).

(iii) In which groups of the periodic table are they

located?

(iii) What will be the nature of oxide of element Y?

Identify the nature of bonding in the compound

23. A group of elements in the periodic table are given

formed.

below (boron is the first member of the group and

(iv) Draw the electron dot structure of the divalent

thallium is the last).

halide.

(NCERT Exemplar)

Boron, aluminium, gallium, indium, thallium

29.

(i) Using the part of the periodic table given below

the atomic number of the element belonging to

answer the questions that follows:

same group and present in fifth period ?

(ii) Name the elements present in the first period of the

Groups →

modern periodic table.

Periods ↓

(iii) Atoms of different elements with same number of

shells are placed in the same period. Explain.

(iv) What is the electronic configuration of the element

Li Be B C N O F Ne

present in third period and belongs to group 15 ?

Na Mg Al Si P S Cl Ar

(v) How many elements are present in mdoern periodic

K Ca

table ?

31.

Read the following and answer the questions from (i)

(a) Na has physical and chemical properties similar to

to (v) given below

which element(s).

(b) Write the electronic configuration of N and P.

Valency is the combining capacity of an atom of an

Which one of these will be more electronegative

element to acquire noble gas configuration. If

and why?

depends upon the number of valence electrons

present in outermost shell of its atom. For the

chlorine.

elements of group 1, 2, 13 and 14 valency = numbers

(ii) The neutral atom of an element E consists 12

of valency electrons(s), whereas for the elements of

electrons in its atoms.

group 15 onwards valency = 8 − valence electrons.

(a) In which period and group is E placed?

The concept of valency is simple and rationalise the

(b) Name the element E.

atomic composition of a large number of compounds.

Yet, in many chemistry courses, it is sidelined in

achieve noble gas configuration ?

favour of electronic theories of bonding, which are

(d) What will be the nature of oxide (acidic/basic) of E?

more difficult. When the theory of valency was

Justify your answer.

devised, chemists thought that all compounds were

(e) Write the formulae of chloride of E.

molecular. We now known that many are

^● Case Based Questions

non-molecular, i.e. they comprise a large number of

atoms bound together in a continuous framework.

30. Read the following and answer the questions from (i)

The theory can however be adapted to include

to (v) given below

non-molecular compounds.

Modern periodic law states that the physical and

The atomic number and valence of element A, B, C,

chemical properties of the elements are periodic

D and E are given in below table.

function of their atomic radius. When these elements

were arranged in the increasing order of their atomic

Elements Atomic number Number of valence electron

number, the obtained table is called modern periodic

table.

Numerous forms of the periodic table have been

devised form time to time. A new version, which is

most convinient and widely used is the modern

periodic table. This table consist of 18 vertical

columns called groups and 7 horizontal rows,

known as periods. The first period consists of two

(i) What is the valency of element B ?

elements.

(ii) If element C reacts with an element D, which type

The subsequent period consist of 8, 8, 18, 18 and 32

of compound they will form.

elements respectively. The seventh period is

(iii) What is the name of element E ?

incomplete and like the sixth period would have

(iv) Element A belongs to which period in the modern

maximum of 32 electrons.

periodic table ?

(i) An element belongs to group 17. It is present in

(v) Among A, C, D and E, which element belongs to

third period and its atomic number is 17. What is

group 17 ?