MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

According to molecular orbital theory, the electronic configurations of the given molecules are written to determine the presence of unpaired electrons. Li _2 (6 electrons): _ 1s ^ 2 _ 1s ^ *2 _ 2s ^ 2 Since all electrons are paired, it is diamagnetic. N _2 (14 electrons): _ 1s ^ 2 _ 1s ^ *2 _ 2s ^ 2 _ 2s ^ *2 _ 2p_x ^ 2 _ 2p_y ^ 2 _ 2p_z ^ 2 Since all electrons are paired, it is diamagnetic. O _2 (16 electrons): _ 1s ^ 2 _ 1s ^ *2 _ 2s ^ 2 _ 2s ^ *2 _ 2p_z ^ 2 _ 2p_x ^ 2 _ 2p_y ^ 2 _ 2p_x ^ *1 _ 2p_y ^ *1 Due to the presence of two unpaired electrons in the ^ * antibonding molecular orbitals, O _2 is paramagnetic. F _2 (18 electrons): _ 1s ^ 2 _ 1s ^ *2 _ 2s ^ 2 _ 2s ^ *2 _ 2p_z ^ 2 _ 2p_x ^ 2 _ 2p_y ^ 2 _ 2p_x ^ *2 _ 2p_y ^ *2 Since all electrons are paired, it is diamagnetic. Answer: O _2