Inert pair effect-definition-examples-cause and consequences

 
·        What is inert pair effect in chemistry ?

Inert pair effect is generally exhibited by some heavier nucleus p-block elements [ such as, Tl, Sn, Pb, Bi, Po etc ] with common molecular formula ns² np^1-6 .

These elements have a less tendency to leave their outer most s-electrons at the time of chemical reaction.

That is, the electron present in the outer most s-orbital , does not participate in the formation of a chemical bond.

The tendency of this two s-electron to stayed inert, is called inert paireffect.

·        Inert pair effect examples in chemistry

Some p-block elements, such as thullium(Tl),polonium(Po), tin ( Sn ), lead (Pb), bismuth ( Bi ) etc exhibit Inert pair effect .

The ‘5s’ electron of tin and ‘6s’ electrons of lead and bismuth have a tendency to main inert due to inert pair effect.

·        What is the cause of inert pair effect in chemistry

Some p-block elements, such as, Polonium (Po),tin( Sn ), lead(Pb) and bismuth ( Bi ), exhibit variable electro-valency due to inert pair effect.

In this type of elements, the main valency is equal to the number of electrons present in the p-sub shell of the outer most shell.

From their electronic arrangement, it has been found that, these type of elements contain inner ‘d’ or ‘f’ electrons.

Now, due to poor shielding effect of ‘d’ or ‘f’ orbitals, the effective nuclear charge on outer most ‘s’-electrons act strongly.

That is, the nucleus bind or pull the ‘s’-electrons strongly.

Consequently, this two ‘s’-electrons show a lesstendency to participate in 

chemical reaction. That is, the two ‘s’-electrons remain inert basically.

·        What is consequences of inert pair effect in chemistry

As a result of inert pair effect, many physical and chemical properties of the relating elements become changes. 

The change of properties of elements and compounds due to inert pair effect are discussed below.

( I )  Stability of elements and compounds changes due to inert pair effect.

For example, SnCl₂ compound is more stable than SnCl4compound.

Because, in the formation of SnCl₂ compound, ‘Sn’ metal utilize two ‘5p’-electrons only.

While, in the formation of SnCl₄ compound, ‘Sn’ metal used both ‘5s’ and ‘5p’ electrons.

But, ‘5s’ electron of ‘Sn’ is not available for compound formation due to inert pair effect. Hence, SnCl₄ compound becomes unstable. 

( II ) Inert pair effect cause the variable valency of elements.

For example, both tin and lead show +2 and +4 oxidation state due to inert pair effect. ‘Tl’ element shows +3 and +1 oxidation state for same cause.

( III ) Inert pair effect, influence the oxidizing and reducing properties of compounds.

For example, +5 oxidation state of Bi is less stable than +3 oxidation state of  bismuth element. 

For this reason, Bi ( V ) compound, [ BiF₅ ] act as a strong oxidizing agent .

It oxidized the other reducing substance readily, and changes its oxidation state from +5 to more stable +3.

 (  IV ) Inert pair effect, affect their melting and boiling point of elements.

For example, the melting and boiling point of polonium [Po] is less than ‘Te’ .

Generally, the melting and boiling point of group 16^th elements increase with increase their atomic number from down the group.

Now, ‘Po’-element contain maximum number of ‘d’ and ‘f’ electrons. So, the inert pair effect becomes more effective for ‘Po’ than ‘Te’ .

As a result, the ‘6s’-electron of ‘Po’ is less available than ‘5s’-electron of ‘Te’.

Hence, in case of polonium, the inter-atomic Vander waal’s force of attraction is than tellurium .

Consequently, the melting and boiling point of polonium is less than tellurium.

Summary:

·        What is inert pair effect in chemistry ?

·        Examples of inert pair effect in chemistry

·        What is the cause of inert pair effect in chemistry ?

·        What is consequences of inert pair effect in chemistry ?

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