Ethene is a covalent compound in which two CH2 units are bound together by a C=C double bond. Though internal bonds are quite strong, the intermolecular forces of attraction are very feeble, as a result, molecule to molecule separation becomes quite easy and it is a gas at room temperature. Sodium chloride, on the contrary, is an ionic compound formed by the association of Na+ and Cl- ions, held by electrostatic force of attraction. This force is nondirectional in nature and as a result forms ionic conglomerates of alternate Na+ and Cl- ionsfrom every direction resulting in giant 3-dimensional ionic assemblies. Hence separation of a single NaCl unit requires huge investment of energy, and as such NaCl is a high melting solid.