How are covalent bonds formed ?

A covalent bond forms when the difference between the electronegativities of two atoms is too small for an electron transfer to occur to form ions. Shared electrons located in the space between the two nuclei are called bonding electrons. The bonded pair is the “glue” that holds the atoms together in molecular units. Covalent bonds, which hold the atoms within an individual molecule together, are formed by the sharing of electrons in the outer atomic orbitals. The distribution of shared as well as unshared electrons in outer orbitals is a major determinant of the three-dimensional shape and chemical reactivity of molecules.

Explanation: