Question

Which of the following order is wrong?
(a) NH₃ < PH₃ < AsH₃ – Acidic
(b) Li < Be < B < C – First IP
(c) Al₂O₃ < MgO < Na₂O < K₂O – Basic
(d) Li⁺ < Na⁺ < K⁺ < Cs⁺ – Ionic radius

Answer 1

Wrong order in given question is- (b) Li < Be < B < C – First IP

Acidic character follows the trend of increasing across a period and decreasing down the group. Option fourth shows ionic radius, which increases down the group.

Ionisation potential is the energy required to remove an electron from an atom. Beryllium has electronic configuration 1s² 2s². Boron has electronic configuration 1s² 2s² 2p¹.

Since beryllium has completely filled orbitals while boron does not have.

This imparts stability and more attraction between electrons and nucleus, thus increasing required amount of energy to remove electron.

Hence, order should be Li < B < Be < C.