How do I calculate the bond order for H2- and H2+?

1 Answer
Truong-Son N.
Apr 1, 2017

I'm assuming you mean #"H"_2^(-)# vs. #"H"_2^(+)#. Well, build the molecular orbital (MO) diagram. Each hydrogen atom contributes one electron, and thus, #"H"_2^(-)# has three electrons while #"H"_2^(+)# has one.

Each hydrogen atom contributes one #1s# atomic orbital, and thus, the orbitals overlap according to MO theory to form one #sigma_(1s)# and one #sigma_(1s)^"*"# MO by conservation of orbitals.

If you calculate their bond order, you get:

#"BO"_(H_2^(+)) = 1/2("Bonding" - "Antibonding")#

#= 1/2(1-0) = 1/2#

#"BO"_(H_2^(-)) = 1/2("Bonding" - "Antibonding")#

#= 1/2(2-1) = 1/2#

So, neither is more stable than the other. But of course, they are less stable than #"H"_2#. What does bond order mean in terms of bond strength?

Related questions
See all questions in Molecular Orbital Theory
Impact of this question
115778 views around the world
You can reuse this answer
Creative Commons License