Determine the molecular geometry for the following ion of NH4+, otherwise known as the ammonium ion. So, nitrogen is in group 5A, so we have 5 valence electrons. Hydrogen is in group 1A and there are 4 of them. Then, remember a plus one charge means we've lost an electron, so we'd subtract this from the total. That means we have 8 total valence electrons. Nitrogen will go in the center because hydrogen can never go in the center. Hydrogen only makes single bonds. Remember, each covalent bond that we just drew represents 2 valence electrons. So, we've just used all 8 of our electrons leaving us with none left. Because it's an ion, we put it in brackets and the charge in the top right corner.
At this point, we would say that our central element has connected to it 4 bonding groups, and it has 0 lone pairs. Remember, when you have 4 bonding groups and 0 lone pairs, your molecular geometry would be tetrahedral. So, we'd say here that the molecular geometry for the ammonium ion is tetrahedral. If we wanted to draw it in the correct way with our visual representation, it would look closer to something like this. The shape's a little bit weird in drawing when you look at it, so it's okay if you want to draw it as the first option that I drew. And again, you'd still put it in brackets with the charge in the top right corner.