Question

Given below are two statements. One is labelled as
Assertion A and the other is labelled as Reason R.
Assertion A : The first ionization enthalpy for oxygen is lower than that of nitrogen.
Reason R : The four electrons in $2 p$ orbitals of oxygen experience more electron-electron repulsion.
In the light of the above statements, choose the correct answer from the options given below.

• A. Both A and R are correct and R is the correct explanation of A.
• B. Both A and R are correct but R is NOT the correct explanation of A.
• C. A is correct but R is not correct.
• D. A is not correct but R is correct

Answer 1

Answer: (A)

Ionisation energy $= N > O$.
In oxygen atom, 2 of the $42 p$ electrons must occupy the same $2 p$ orbital resulting in an increased electron electron-repulsion.