Question

1. Consider the H2* ion and respond to the following questions. (a) Sketch the unoccupied MO of Hat and tell whether this orbital has a node. If yes, sketch (or describe) the surface. HH (b) How does the energy of the o-bonding MO of H2* compare to that of the 1s orbital of hydrogen? (c) Would you expect Hal to act as an oxidant or as a reducing agent toward the Halon in a chemical reaction? Briefly explain

Answer 1

Answer to 1-a:

nodal plane 01 1S H 十 01S

The antibonding MO means the destructive interference between two waves (from two atomic orbitals of two hydrogens). This decreases in the electron density in the internuclear electron probability density. Thus, a node is created where the elctron density is zero.

Answer to part 1-b:

As it can be seen from the above diagram, the $\sigma _{1S}$ orbital has lower energy than the energy of the 1S orbital of the H atom.

Answer to part 1-c:

The electronic configuration according to the MO diagram for H₂⁺ ion is  
Osois
. The electronic configuration according to the MO diagram for H₂^- ion would be  
oisois
. The electron in the antibonding orbital in the H₂^- has higher energy than the singly occupied MO (SOMO) of the H₂⁺. Thus, transfer of one electron from H₂^- ion  to the SOMO ofthe H₂⁺ ion is favorable. Thus, H₂⁺ acts as an oxidizing agent and H₂^- acts as an reducing agent in the chemical reaction between these two ions.