Why are covalently bonded materials generally less dense than metallically or ionically bonded ones

Explanation:

It is known that ionic compounds are formed by transfer of electrons from one atom to another. And, during this type of bonding there occurs long range of bonding structure due to the nature of ionic bonds.

As these also contain opposite charge hence, they are more tightly packed with each other.

Whereas in covalent bonding the atoms tend to share electrons due to which they are not tightly packed with each other. As a result, empty spaces are created between the bonding structure which tends to reduce the density of the material.

Therefore, covalently bonded materials generally less dense than metallically or ionically bonded ones.