What are bonding and non bonding pairs and their relation to the Lewis symbol and molecular shapes?
Bonding pairs of electrons are that which are shared between two atoms, ie in H2O two H atoms are bonded to the central O, the bond is caused by the sharing of electrons. If you have non-bonding (or long) pairs, they repel the bonded pairs (in order to best reduce electron repulsion because like charges repel each other). In water there are two lone pairs, because the H-O bond is only singular, these lone pairs push or repel the O-H bonds down, to 104.5 degree angles. This results in the molecule being bent in shape (and consequently polar). However, CH4 (Methane) has no lone pairs to repel the bonded ones and as such is arranged in a tetrahedral shade, 109.5 degree bond angles, which is symmetrical and non-polar.
