Chemical Bonding and Molecular Structure · Question 4

Regarding the molecular orbital (MO) energy levels for homonuclear diatomic molecules, the INCORRECT statement(s) is(are)

1. Bond order of Ne2 is zero.
2. The highest occupied molecular orbital (HOMO) of F2 is σ-type.
3. Bond energy of O2+ is smaller than the bond energy of O2.
4. Bond length of Li2 is larger than the bond length of B2.

Answer

(2) The highest occupied molecular orbital (HOMO) of F2 is σ-type., (3) Bond energy of O2+ is smaller than the bond energy of O2.

Solution

(A) Ne2: 10 bonding and 10 antibonding electrons, so B.O. = 0. This is correct.

(B) F2: ...( 2p)4( * 2p)4, so the HOMO is * (π-type). The statement is incorrect.

(C) B.O. of O2+ = 2.5 and of O2 = 2. A higher bond order means a larger bond energy, so the statement is incorrect.

(D) Li2 (B.O. 1, large 2s orbitals, about 267 pm) is longer than B2 (B.O. 1, about 159 pm). This is correct.

Answer: (B), (C)