Question

Covalent compounds have low melting point because:
(A) Covalent molecules have definite shape
(B) Covalent bond is weaker than ionic bond
(C) Covalent bond is less exothermic
(D) Covalent molecules are held by weak Vander waals forces of attraction.

Answer 1

Hint:To answer this question we should know about the forces present in covalent molecules which bind them together. Covalent molecules are held together by weak forces. Melting point is defined on the interactions of the molecules, not the bonds present in them.

Complete step by step solution:
> First let’s try to understand what is melting point:
> The melting point of a substance is defined as the temperature at which the forces binding the molecules together are overcome and the substance gets converted into its liquid state.
> There is no breaking of bonds when a substance melts. Only the molecular forces of attraction are broken by which the molecules are held together.
- Now, if the molecular interactions will be weak then they can be easily overcome on providing energy. Hence, weaker the forces of interaction among the molecules slower will be the melting point of the substance.
> Covalent molecules are held by Vander waals forces of interaction. These forces are weaker in nature. Hence, the melting point of covalent compounds is low in general.
Hence, the answer to the given question is option (D)

Note:The covalent bond is present between the atoms. It is a comparatively strong bond but the melting point is not dependent on the covalent bond. It is dependent on the inter-molecular interactions between molecules.