Question

Assertion: Third ionization energy of phosphorus is larger than sulphur.
Reason: There is a larger amount of stability associated with filled $s$- and $p$- sub-shells (a noble gas electron configuration) which corresponds to having eight electrons in the valence shell of an atom or iron.

• A. If both A and R are correct and R is the correct explanation of A.
• B. If both A and R are correct but R is not the correct expalnation of A.
• C. A is true but R is false.
• D. A is false but R is true.
• E. A and R both are false.

Answer 1

Answer: (D)

Electrons configuration ${ }_{16} S ^{2+}=1 s ^{2} 2 s ^{2} 2 p ^{6} 3 s ^{2} 3 p ^{2}$ and ${ }_{15} P ^{2+}$ $=1 s ^{2} 2 s ^{2} 2 p ^{6} 3 s ^{2} 3 p ^{1}$.
Sulphur has higher nuclear charge and smaller size than that of phosphorus so $IE _{3}$ of $S > P$