Carbon can neither lose four of its electrons nor gain four electrons as both the processes
require extra amount of energy and would make the system unstable. Therefore, it
completes its octet by sharing its four electrons with other carbon atoms or with atoms of
other elements. The bonds that are formed by sharing electrons are known as covalent
bonds. In covalent bonding, both the atoms share the valence electrons, i.e., the shared
electrons belong to the valence shells of both the atoms.
Here, carbon requires 4 electrons to complete its octet, while each hydrogen atom requires
one electron to complete its duplet. Also, chlorine requires an electron to complete the
octet. Therefore, all of these share the electrons and as a result, carbon forms 3 bonds
with hydrogen and one with chlorine.

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