Why is C{l_2} a covalent bond?

The notation "C{l_2}" appears to be a formatting error or misunderstanding. It's not a standard representation of a chemical compound or bond. However, I can provide information on covalent bonds and the diatomic molecule Cl2 (chlorine gas), which is a common example of a covalent compound.

Covalent bonds are formed when two or more atoms share electrons to achieve a more stable electron configuration. In a covalent bond, the electrons are shared between the atoms involved. Covalent bonds typically occur between nonmetals, as nonmetals tend to have similar electronegativities (the ability to attract electrons) and therefore share electrons more equally.

Chlorine gas (Cl2) is a diatomic molecule consisting of two chlorine atoms, each of which has seven electrons in its outermost electron shell. Both chlorine atoms share one electron with each other to complete their outer electron shells. This sharing of electrons results in the formation of a covalent bond, specifically a "single covalent bond" or "sigma bond" between the two chlorine atoms.

The sharing of electrons in Cl2 allows both chlorine atoms to achieve a more stable electron configuration similar to that of noble gases. This is the essence of covalent bonding: atoms sharing electrons to achieve a more stable state.