What is the key principle behind VSEPR theory

Minimizing repulsion by maximizing the bond angles

Explanation:

VSEPR is defined as 'valence shell electron pair repulsion' theory. The key principle is that repulsion of adjacent lone pairs of electrons or the electrons that are shared within a bond creates bond angles.

The bond angles are maximized in order to minimize the repulsion in the most stable geometrical shape of the molecule.

That said, in VSEPR theory we tend to achieve the greatest possible angles between the bonds and lone pair electrons in order to obtain the lowest repulsion between them.