How do you determine the shape and bond angle of an ammonia molecule?

Firstly, how many electrons does nitrogen have in its outer shell?... Nitrogen is in group 5, so 5.How many more electrons does nitrogen need to give it a full outer shell?... 8 electrons provide a full outer shell, so it needs 3 more. Therefore each nitrogen atom makes one covalent bond with 3 hydrogen atoms.So what is the formula of ammonia?... NH3. 3 of the nitrogens 5 outer electrons are involved in covalent bonds with hydrogen atoms, so how many lone pairs are there?... There are 2 electrons left over in the outer shell so one lone pair.Therefore there are 3 bonding pairs and 1 lone pair, so what shape is the molecule?... Triangular pyramid.What is the bond angle?... There are four pairs of electrons so the initial bond angle is 109.5 degrees, however lone pairs decrease the angle by 2.5 degrees each. There is one lone pair so the bond angle is 109.5-2.5= 107 degrees.