 # How to draw Molecular Orbital Diagram of Li

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Lithium belongs to group 1 ( alkali metals), period 2 s-block element of the periodic table. Lithium is represented by the symbol “Li”.

The atomic number of Lithium (Li ) is 3 and the mass number is 6.941.

## Li Electronic Configuration:

The distribution of electrons in lithium electronic shells is as follows:

K shell = 2 electrons

L shell = 1 electron

so the electron configuration is :

The electronic configuration of the Li atom is 1s2 2s1.

## How do draw the Molecular Orbital Diagram of Lithium molecule (Li2)?

According to the molecular orbital theory, the molecular orbital diagram of the lithium molecule is shown below:

The 2 electrons are present in σ 2s orbitals.

The antibonding molecular orbital σ*2 s is empty.

Thus

Bond order = Number of electrons in BMO – Number of electrons in ABMO /2

Bond order = 2-0

2

Bond order = 1

Bond order 1 shows that there is a single covalent bond between the lithium atoms in the Li2 molecule.

### How to draw the molecular orbital diagram of Li2, Li2 +, Li2 –?

In the case of Li2 +, the 1 electrons are present in σ 2s orbitals.

The antibonding molecular orbital σ*2 s is empty.

Thus

Bond order = Number of electrons in BMO – Number of electrons in ABMO / 2

Bond order = 1-0

2

Bond order = 0.5

Similarly,

In the case of Li2 -, the 2 electrons are present in σ 2s orbitals.

The antibonding molecular orbital σ*2 s contains 1 electron.

Thus

Bond order = Number of electrons in BMO – Number of

electrons in ABMO/ 2

Bond order = 2-1

2

Bond order = 0.5

### Arrange the following species in increasing order of stability:Li2, Li2 +, Li2 –

Since the bond order of Li2 is higher than Li2 + and Li2 -. Therefore, Li2 has stronger single covalent bonding. Thus lithium molecule (Li2) is more stable.

## Li2 + is more stable as compared to Li2 – :

Li2 + and Li2 ions have the same bond order ( 0.5).

But Li2 has more electrons in higher energy antibonding molecular orbital as compared to Li2 +.

Thus Li2 + is more stable than Li2.

so the increasing order of stability is:

Li2 > Li2 + > Li2

Trick to Calculate Bond Order :

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### 1 thought on “How to draw Molecular Orbital Diagram of Li2 , Li 2+ , Li2 –”

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