Compare distances to the central atom in the following related compounds and discuss what might be the reason for any trends that you see. (Consider one of the F atoms in F2 to be central.) Pertinent discussions are shown in brackets.

1. CH₄, NH₃, H₂O, HF [11bcd]
2. CF₄, NF₃, OF₂, F₂ [13d]
3. BH₄^–, CH₄, NH₄+ [31a,37a]
4. BeF₄₂^–, BF₄^–, CF₄ [33b,39b]
5. PH₃, SiH₄, H₂S [19cd]
6. NHF₂, CH₂F₂, OF₂ [17bc]
7. PHF₂, SF₂, S(CH₃)₂ [25ab]
8. PF₃, POF₃ [21c]
9. NF₃, CHF₃ [13c]
10. IO₃^–, XeO₃, IO₄-, XeO₄ [27ab,77]