Prior to 2000, many drugs that formed a covalent bond with targets did so non-selectively, which often led to undesired side effects when compared to non-covalent drugs. This led to the belief that ...

The most widely used scale is the thermo-chemical Pauling’s scale ... In an oxygen (O2) molecule, both atoms have the same electronegativity. The electrons in the covalent bond are shared equally ...