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Bond Lengths

Why is it that the fewer electrons there are, the longer the bond length? I have a question were I need to explain why the bond length in (H2)+ is longer than in H2. Is it reduced electron shielding of the nuclei so they repel each other more strongly?

Bond strength is reduced because there is reduced overlap of electron orbitals right?
Reply 1
Avatar for shengoc
shengoc
12
FinalFan3
Why is it that the fewer electrons there are, the longer the bond length? I have a question were I need to explain why the bond length in (H2)+ is longer than in H2. Is it reduced electron shielding of the nuclei so they repel each other more strongly?

Bond strength is reduced because there is reduced overlap of electron orbitals right?


You need to be careful when you said the fewer electrons there are, the longer the bond length. If you have done molecular orbital theory, this will all be explained nicely by bond order.

Bond order = 1/2(number of bonding electrons - number of antibonding electrons)

The higher the bond order, the stronger are the bonds, therefore generally the shorter are the bonds and vice versa.

For H2 and H2+, H2 has two electrons that occupy the bonding electrons, no anti bonding electrons, bond order = 1, whereas for H2+, bond order = 1/2, hence bond strength of H2+ is weaker and hence the bond is longer than H2.
Reply 2
Avatar for Kaeroll
Kaeroll
As shengoc rightly says, bond length is not correlated to number of electrons but strength of bond, which is determined largely by the number of electrons in bonding orbitals.
Reply 3
Avatar for FinalFan3
FinalFan3
OP
13
OK thanks. I have to explain about the bond length and strength, so can I just say because the bond is weaker it is therefore longer?
Reply 4
Avatar for shengoc
shengoc
12
FinalFan3
OK thanks. I have to explain about the bond length and strength, so can I just say because the bond is weaker it is therefore longer?


Weaker bonds are essentially longer.
Reply 5
Avatar for alveolus
alveolus
11
I was going to add my twopennyworth, but you seem to get the jist. More bonding electrons means stronger bond, H2 can have up to 2 bonding electrons, hence 2 is the best, 1 is not as good.

Stronger bonds are shorter.

cool

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