Which one of the following is a covalent compound?

Covalent compounds are formed by the sharing of electrons between atoms, typically non-metals, to achieve a stable electron configuration [2]. Silicon carbide (SiC), also known as carborundum, is a classic example of a covalent network compound where covalent bonding extends throughout the entire structure. In this lattice, each silicon atom is bonded to four carbon atoms, resulting in a very hard material with a high melting point. In contrast, calcium oxide (CaO), sodium nitride (Na3N), and sodium sulphide (Na2S) are classified as ionic compounds [2]. These are formed by the transfer of electrons from electropositive metals (like sodium or calcium) to electronegative non-metals, resulting in electrostatic forces of attraction between ions [2]. Carbon's unique ability for catenation and tetravalency allows it to form such stable covalent bonds with elements like silicon [2].

Sources

1. [2] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > What you have learnt > p. 77
2. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.2 VERSATILE NATURE OF CARBON > p. 62