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### Topic: energy diagrams and interatomic distances  (Read 8007 times)

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#### studygirl

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##### energy diagrams and interatomic distances
« on: June 30, 2005, 10:07:53 PM »
The interatomic disatances in N2, and N2+ are 0.112 and 0.129nm; in Cl2 and Cl2+ they are 0.199 and 0.189nm. Using the Mo theory, explain why the N2+ cation has a longer bond length than N2, while the Cl2+ cation has a shorter bond legnth than Cl2. Use energy level diagrams in your explanation.
b)give the electronic configuration of the N2+ cation..

okay so firstly i know that the electrons in the bonding molecular oribtitals are responsible for holding the atoms together,N+2 should have a weaker, and, therefore, longer bond than N2. But how do i use the energy level diagram? can some one please explain how to draw one?
and why is Cl2+ shorter bond?

what is the difference between the electronic configuration of N2+ and electron configuration? can someone please shed some light on this....how to approach. thanks a lot

#### Winga

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##### Re:energy diagrams and interatomic distances
« Reply #1 on: July 01, 2005, 12:40:46 AM »
First, draw out the MO diagrams of N2, N2+, Cl2 and Cl2+.
The energy level diagrams you mentioned should be the MO diagrams, but I'm not sure.

Then, calculate the bond order of those molecules and you will find out the reason of bond length differences.

Bond order:
(no. of e- in bonding orbitals - no. of e- in anti-bonding orbitals)/2
or
no. of e- pairs in bonding orbitals - no. of e- pairs in anti-bonding orbitals

About the e- configuration of molecules (molecular ions).
It should be like this...
e.g. N2
(sigma1)2 (sigma*1)2 (pi)4 (sigma2)2

I am not sure this one is the standard form because I find that some books use sigma1u, sigma1g to instead.

#### studygirl

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##### Re:energy diagrams and interatomic distances
« Reply #2 on: July 03, 2005, 08:34:39 PM »
hey i am having huge problems understanding how to draw molecular oribitals, thus having problems with this question

#### Winga

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##### Re:energy diagrams and interatomic distances
« Reply #3 on: July 04, 2005, 12:14:38 AM »
Read some reference books, you need to have a basic knowledge about MO theory.

You can just remember the pattern of the lines (MOs).

#### arnyk

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##### Re:energy diagrams and interatomic distances
« Reply #4 on: July 04, 2005, 07:00:20 PM »
Does it matter that Cl is in Period 3, giving it a relatively larger atomic radius?