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ICSE Class 10 Chemistry Question 9 of 28

Chemical Bonding — Question 21

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Question

Question 18

Explain the terms :

(a) Lone pair of electrons

(b) Coordinate bond

Explain diagrammatically the lone pair effect of:

(a) The nitrogen atom of the ammonia molecule leading to the formation of ammonium ions [NH4]+

(b) The oxygen atom of the H2O molecule leading to formation of hydronium [H3O]+ and hydroxyl ions [OH]-

Answer

(a) Lone pair of electrons — They are a pair of electrons not shared with any other atom.

(b) Coordinate Bond — It is a type of covalency which involves one of the combining atoms contributing both of the shared electrons. i.e., a bond formed by a shared pair of electrons with both electrons coming from the same atom.

(a) Formation of ammonium ions [NH4]+

Explain diagrammatically the lone pair effect of the nitrogen atom of the ammonia molecule leading to the formation of ammonium ions. Chemical Bonding, Simplified Chemistry Dalal Solutions ICSE Class 10

In ammonia, the 'N' atom contains one lone pair of electrons after completing it's octet. This lone pair is accepted by the hydrogen ion of water leading to the formation of a coordinate covalent bond:

−N∣∣→H-\overset{|}{\underset{|}{\text{N}}} \rarr \text{H}

(b) Formation of hydronium (H3O)+ and hydroxyl ions [OH]-

Explain diagrammatically the lone pair effect of the oxygen atom of the H2O molecule leading to formation of hydronium and hydroxyl ions. State the type of bonding present in it. Chemical Bonding, Simplified Chemistry Dalal Solutions ICSE Class 10

In water, the 'O' atom contains two lone pairs of electrons after completing it's octet. These lone pairs are accepted by the hydrogen ion leading to the formation of coordinate covalent bond:

−O∣→H-\overset{|}{\text{O}}\rarr\text{H}