Chemistry Class-11: Chapter –3. Classification of Elements and Periodicity in Properties-Part – 7

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Question: 40

How does the metallic and non metallic character vary on moving from left to right in a period?

Answer:

Metallic character decreases and non metallic character increases in moving from left to right in a period. It is due to increase in ionisation enthalpy and electron gain enthalpy.

Question: 41

The radius of cation is less than that of atom. Give reason.

Answer:

Decrease of one shell.

Question:

Among alkali metals which element do you expect to be least electronegative and why?

Answer:

Electronegativity decreases in a group from top to bottom. Thus, caesium is the least electronegative element.

IV. Matching Type

Question: 43

Match the correct atomic radius with the element.

Element and Atomic Radius
Element and atomic radius

Element

Atomic radius (pm)

Be

74

C

88

O

111

B

77

N

66

Answer:

Question: 44

Match the correct ionisation enthalpies and electron gain enthalpies of the following elements.

Elements and Enthalpy
Elements and enthalpy

Elements

i

Most reactive non metal

A

419

ii

Most reactive metal

B

iii

Least reactive element

C

Iv

Metal forming binary halide

D

Answer:

Question: 45

Electronic configuration of some elements is given in Column I and their electron gain enthalpies are given in Column II. Match the electronic configuration with electron gain enthalpy.

Electronic Configuration and Enthalpy
Electronic Configuration and Enthalpy

Column (I)

Column (II)

Electronic Confguration

Electron gain enthalpy/kJ

(i)

A

(ii)

B

(iii)

C

(iv)

D

Answer:

V. Assertion and Reason Type

In the following questions a statement of Assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.

Question: 46

Assertion (A): Generally, ionisation enthalpy increases from left to right in a period.

Reason (R): When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate for the increased attraction of the electron to the nucleus.

(i) Assertion is correct statement and reason is wrong statement.

(ii) Assertion and reason both are correct statements and reason is correct explanation of assertion.

(iii) Assertion and reason both are wrong statements.

(iv) Assertion is wrong statement and reason is correct statement.

Answer: (ii)

Question: 47

Assertion (A): Boron has a smaller first ionisation enthalpy than beryllium.

Reason (R): The penetration of a electron to the nucleus is more than the electron hence 2p electron is more shielded by the inner core of electrons than the electrons.

(i) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(ii) Assertion is correct statement but reason is wrong statement.

(iii) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(iv) Assertion and reason both are wrong statements.

Answer (iii)

Question: 48

Assertion (A): Electron gain enthalpy becomes less negative as we go down a group.

Reason (R): Size of the atom increases on going down the group and the added electron would be farther from the nucleus.

(i) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(ii) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(iii) Assertion and reason both are wrong statements.

(iv) Assertion is wrong statement but reason is correct statement.

Answer: (iv)