97.1º 98.2º 99º

Cl, the most electronegative of the halogens in this series, pulls shared electrons the most strongly away from Sb, reducing electron density near Sb. The consequence is that the lone pair exerts the strongest influence on shape in SbCl 3 .

102º 100º 99º

Phosphorus is the most electronegative of the central atoms. Consequently, it exerts the strongest pull on shared electrons, concentrating these electrons near P and increasing bonding pair-bonding pair repulsions–hence, the largest angle in PI 3 . Sb, the least electronegative central atoms, has the opposite effect: Shared electrons are attracted away from Sb, reducing repulsions between the Sb–I bonds. The consequence is that the effect of the lone pair is greatest in SbI 3 , which has the smallest angle.

Atomic size arguments can also be used for these species. Larger outer atoms result in larger angles; larger central atoms result in smallest angles.