There are four regions of electron density around sulfur in SCl2 consisting of two sulfur-chlorine bonds and two lone pairs, which repel each other resulting in a 109 degree bond angle for maximum stability. Similarly, there are three regions around oxygen in O3 comprising one single bond, one double bond, and one lone pair, also repelling to achieve a 120 degree bond angle providing greatest stability.

1.    Tells us 4 regions Tells us 3 regions As shown in Lewis diagrams above:  There are 4 regions of electron density around the S in SCl 2 2(S-Cl) and two lone pairs of electrons  These four regions repel each other to gain maximum stability. This results in the 109 0 bond angle observed.  There are 3 regions of electron density around the O in O 3 (1 O-O), 1(O=O) and one lone pair of electrons.  These three regions repel each other to gain maximum stability. This results in the 120 0 bond angle observed.