Importance and limitation of valence bond theory

Valence bond theory, despite the specific limitations catalogued in the next section, introduced five genuinely new ideas into the theory of chemical bonding that are still used today: (i) the DELOCALISATION of a bonding electron pair, spread over the two nuclei it bonds rather than sitting on either nucleus alone; (ii) the SHIELDING effect that inner electrons have on outer/bonding electrons; (iii) the notion of COVALENT CHARACTER as a distinct, quantifiable property of a bond; (iv) the complementary notion that a covalent bond can itself carry PARTIAL IONIC CHARACTER, when the two bonded atoms differ in electronegativity; and (v) the concept of RESONANCE, together with the connection be …