Dipole moments or polarity happens in molecules when there is an unequal sharing of electrons. For these molecules, both molecular shape and bond polarity can affect their overall polarity.
When the central element has no lone pairs and has the same surrounding elements then usually the molecule is nonpolar.
There are 3 cases when a molecule is non-polar:
1. Molecular shapes that are seen as perfect (symmetrical) will be non-polar if the surrounding elements are the same. These are:
AX4E2- square planar
2. The compound has only carbons and hydrogens
3. A non-metal is by itself or connected to copies of itself.
When the central element has lone pairs then we must use element dipole arrows and lone pair dipole arrows to determine polarity.
Element dipole arrows point towards the more electronegative atom while lone pair dipole arrows point towards the lone pair.
All the compounds have electronegative atoms. Let us then look at the structures and check if polar bonds cancel out.