chemical bonding

How to draw Molecular Orbital Diagram of Li2 ,Li 2+ , Li2 – | Simplest Trick – Chemistry

Do you know !!

Lithium belongs to the 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.

Lithium atom

Li Electronic Configuration:

The distribution of electrons in lithium electronic shells are as follow:

K shell = 2 electrons

L shell = 1 electron

so the electron configuration is :

Electronic configuration of Li atom is 1s2 2s1 .

How to draw Molecular Orbital Diagram of Lithium molecule (Li2) ?

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

The 2 electrons are present in σ 2s orbitals .

The anti bonding 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 Li2 molecule.

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

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

The anti bonding 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,

Incase of Li2 – , the 2 electrons are present in σ 2s orbitals .

The anti bonding molecular orbital σ*2 s contain 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

Recommended video !!

Molecular Orbital Energy level Diagram for Li2, Li2+ ,Li2 – ( in Urdu / Hindi)
Pages: 1 2 3

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s