Bromine will normally form one covalent bond. Bromine, which belongs to group 17 and period four of the Periodic Table, has seven outer shell or valence electrons. When a bromine atom forms a covalent bond with another bromine atom, the atom's outer shell has a full electron configuration.
A full electron configuration, which comprises of eight electrons, ensures the stability of the bond. Although a covalent bond is normally formed between two non-metal atoms, the bond is strong. When two atoms bond together, they form a molecule. A bromine molecule is called a diatomic molecule since it has only two atoms. Other examples that form a diatomic molecule are fluorine and oxygen.