Chemical Bonding Molecular Structure L-7
Chemical bonding molecular structure
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
- He2
- Be2
- There is no bond in Be2 example - Be2 molecule does not exist
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
- B2 - 1s2 , 2s2 2p1
- B.O = 22 = 1
- B2 is not diamagnetic , experimentally B2 paramagnetic
- C2 - it has 12 electrons
Chemical Bonding Molecular Structure L-7
Mixing of orbitals
- Energies of orbitals should be similar
- Symmetries of orbitals should be same
- For Li2 to N2
- Mixing of 2s with 2p orbital
- The mixing of orbitals depend upon effective nuclear charge Z∗
- Z∗ increases from left to right
Chemical Bonding Molecular Structure L-7
Mixing of orbitals
- From Li to F , Z∗ increases , electrons present in different orbitals attracted towards nucleus in differnt ways as a result there is mixing of 2s and 2p orbitals
- From O2 to F2 , Z∗ increases , the gap between 2s and 2p orbital is large so there is no mixing of 2s with 2p orbital
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
For B2−1s22s22p1
- Bond order = 1
- B2 is paramagnetic
For C2 - number of electrons are 12
- Bond order = 24−0 = 2
- C2 is diamagnetic
For N2 - number of electrons are 14
- Bond order = 26−0 = 3
- N ≡ N
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
- For O2 - there are two unpaired electrons example - it is paramagnetic
- According to valence bond theory , O2 is diamagnetic
- So , this is the failure of valence bond theory
- According to MOT , 1 electron is enough for bond formation
- HOMO is (highest occupied molecular orbital)
- LUMO is (lower unoccupied molecular orbital)
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
- O22− O2− O2+
- O2+2electron→ O22−
- For O2
- Bond order = 2
- Bond length = 121pm
- For O22−
- Bond order = 1
- Bond length = 149pm
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
- For O22−
- Number of electrons are 18
- Bond order = 26−4 = 1
- For O2−
- Bond order = 26−3 = 1.5
- O−O = 126pm
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
- For O2+
- Bond order = 26−1 = 2.5
- O−O = 112pm
- O2+ > O2 > O2− > O22−
- 2.5 > 2 > 1.5 > 1 (Bond order)
- 112pm < 121pm < 126pm < 149pm (Bond length)
Chemical Bonding Molecular Structure L-7
Molecular orbital diagram
- Li2 to N2
- O2 to F2
Chemical Bonding Molecular Structure L-7
Thank you
Chemical Bonding Molecular Structure L-7 Chemical bonding molecular structure $\rightarrow$ $\rightarrow$ Chemical bonding molecular structure $\rightarrow$ Molecular orbital diagram $\rightarrow$ Molecular orbital diagram