When two atoms form a covalent bond the electrons in the bonds and non-bonding in the outer shell act as negatively charged clouds thereby repelling each other. To prevent this as much as possible, the electrons in the outer shell are spread out as far as possible in space.

Molecular shapes and bond angles can be predicted using the valence shell electron pair repulsion theory (VSEPR). This theory consists of two rules:

• 1) all lone pairs and all s-bonded electron pairs are arranged as far apart in space as they possible
• 2) bonding pairs do not repel as much as lone pairs

As you can see from the table below, these rules can be used to predict the shape of ions and covalent molecules.