Q47 of 59 Page 35

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.


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


Reason (R) : The penetration of a 2s electron to the nucleus is more than the 2p electron hence


2p electron is more shielded by the inner core of electrons than the 2s 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.


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


Boron has [He]2s22p1 configuration and after donating one electron it attains stable configuration therefore it has smaller first ionisation enthalpy than beryllium which has a completely filled s orbital as it a configuration [He]2s2. As 2p electrons are shielded by the inner electrons so it is easy to remove an electron from these orbitals and their ionisation energy decreases.


More from this chapter

All 59 →
45

Match the electronic configuration with electron gain enthalpy.

 46

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.


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.


 48

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.


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.


 49

Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.