Chemical Bonding and Molecular Structure

Molecular Orbital Theory

MOED (molecular orbital energy diagram) : (from O2 molecule onwards)
\sigma 1s < \sigma^{*}1s <\sigma2s < \sigma^{*}2s < \sigma2p_{z} < \pi2p_{x} = \pi2p_{y} < \pi^*2p_{x} < \sigma^* 2p_{z}

MOED (From N2 molecule onwards)
\sigma 1s < \sigma^{*}1s <\sigma2s < \sigma^{*}2s < \pi2p_{x} = \pi2p_{y} < \pi2p_{z} < \pi^*2p_{x} = \pi^*2p_{y} < \sigma2p_{z}

H2 molecule (2e-)
Bond \ order = \frac{2 - 0}{2}
= 1 (Dia magnetic)

Be2 (8e-)
MOED = σ1s2  σ*1s2 σ2s2 σ*2s2
BO = 0 ⇒ \frac{4 - 4}{2} (can't exist)
dia magnetic

Short cut to determine magnetic nature :

no.of electrons Bond order magnetic character
10 1 P
11 1.5 P
12 2 D
13 2.5 P
14 3 D
15 2.5 P
16 2 P
17 1.5 P
18 1 D


P - Paramagnetic
D - Diamagnetic

Part1: View the Topic in this Video from 0:01 to 9:50

Part2: View the Topic in this Video from 0:59 to 45:55

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