Bonding in Some Homonuclear (Diatomic) Molecules

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11th Chemistry NCERT notes

Hydrogen molecule (H2)

It is formed by the combination of two hydrogen atoms. Each hydrogen atom has one electron in 1s orbital, so, the electronic configuration of hydrogen molecule is

Hydrogen molecule (H2)

This indicates that two hydrogen atoms are bonded by a single covalent bond. Bond dissociation energy of hydrogen has been found = 438 kJ/mole. Bond length = 74 pm

No unpaired electron is present therefore, it is diamagnetic.

Helium molecule (He2)

Each helium atom contains 2 electrons, thus in He2 molecule there would be 4 electrons.

The electrons will be accommodated in σ1s and σ*1s molecular orbitals.

Helium molecule (He2)

He2 molecule is therefore unstable and does not exist.

Lithium molecule (Li2)

Lithium molecule (Li2)

Nature = Diamagnetic, since molecular orbitals are completely filled.

Oxygen molecule (O2)

The orbital configuration of oxygen is

Oxygen molecule (O2)

This means that sixteen electrons are to be filled in the molecular orbital of oxygen molecule (O2.

The molecular orbital configuration

Oxygen molecule (O2)

It may also be written as:

Oxygen molecule (O2)

Nature: Paramagnetic due to the presence of two unpaired electrons.

 

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