Question

The compound which forms a dative bond with ammonia, is:
(A) $ACC{{l}_{4}}$
(B) $BC{{l}_{3}}$
​(C) $MgC{{l}_{2}}$
(D) $NaCl$

Answer 1

Hint: Dative bond can be defined as a type of chemical bond that is formed in between two atoms due to the sharing of the electron pair where only one atom which is present in the molecule gives a shared pair of electron for the formation of a bond. Now we use this concept to the given options and find out the correct option.

Complete Step by Step Solution:
Dative bond is a chemical bond between two atoms in which only one atom provides a shared pair of electrons for bond formation. Only those atoms form dative bonds that have lone pairs of electrons. Dative bond is represented by an arrowhead that points from donor atom to acceptor.

NH₃ molecule: Central atom of NH₃ is nitrogen; it has 5 electrons that form covalent bonds with their H-atoms. Two electrons remain unbonded. These electrons help in the formation of dative bonds.
Example:

Reaction between Boron Trichloride $BC{{l}_{3}}$ and ammonia ($N{{H}_{3}}$) is due to formation of dative bonds.

BCl₃ is electron deficient and ammonia with lone pairs of electrons is electron rich so they form dative bonds. Interconnection between N and B atoms will lead to the favourable lowering of energy of the pair of molecules which have a stabilising effect.
Thus, Option (B) is correct.

Note: At the time of formation of a dative bond the other atom present in the same molecule does not provide electrons for sharing. We said that it is one sided sharing. When there is the formation of the coordinate covalent bond the atoms consist of lone pairs of electrons present in it.