This paper discusses in detail the calculation of bond lengths of organic molecules in the solid state. It describes briefly the effect of electronegativity in covalent bond length. A set of single bond covalent radii and electronegativity values are proposed. Covalent bond lengths calculated by a modified form of the soft sphere equation (which calculated internuclear separation of different Group 1 and Group 2 crystalline salts to a remarkable degree of accuracy) show very good agreement with observed values. The results also show that electronegativity is a major influence on covalent bond lengths and the soft sphere model described here can be used to calculate covalent bond lengths of other organic/bio-organic molecules in different environments that have not yet been experimentally measured.