Question

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

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is D Assertion is incorrect but Reason is correct

$P-151s^{2}2s^{2}2p^{6}3s^{2}3p^3$

$S-161s^{2}2s^{2}2p^{6}3s^{2}3p^4$

$(I{E}_1{)}_P>(I{E}_1{)}_S$ as P is having extra stability due to the half filled orbital. Larger amount of stability is associated with filled s and p subshells which corresponds to having 8 electrons in the valence shell of an atom or ion.