Question

Which one of the following has the coordinate bond?
a.) ${ NH }_{ 4 }{ Cl }$
b.) ${ AlCl }_{ 3 }$
c.) ${ NaCl }$
d.) ${ Cl }_{ 2 }$

Answer 1

Hint: A coordinate bond is a type of covalent bond which is formed between two species in which a shared pair of electrons are donated by one species only but shared by two species.

Complete step-by-step answer:
A coordinate bond is also known as a dative bond.
Firstly, in ${ NH }_{ 4 }{ Cl }$, nitrogen has a lone pair of electrons that are responsible for the formation of coordinate covalent bonds.
Here, three covalent bonds are present between nitrogen and hydrogen, and one coordinate bond is formed between nitrogen and hydrogen.

In ${ AlCl }_{ 3 }$, ionic bonds are present between aluminium and chlorine. Two of these molecules join together to form a dimer.

${ NaCl }$ is an ionic compound that is formed by the transfer of electrons which create ions. Here, the sodium ion is positively charged and the chloride ion is negatively charged.
  

In ${ Cl }_{ 2 }$, covalent bonds are present in between Cl atoms. As both atoms share and hold tightly onto each other’s electrons.

Hence, we can say that a coordinate bond is present in ${ NH }_{ 4 }{ Cl }$.
The correct option is A.

Note: The possibility to make a mistake is that you may choose option D. ${ Cl }_{ 2 }$ has only a covalent bond between its atoms and it joins together to form a dimer.