Carefully compare the angles in the related compounds shown below and discuss what might be the reason for any trends that you see. Pertinent discussions are given in brackets.

1. CH₄, NH₃, H₂O, HF [11bcd]
2. CF₄, NF₃, OF₂, F₂ [13d]
3. BH₄^–, CH₄, NH₄+ [31b]
4. BeF₄₂^–, BF₄^–, CF₄ [33b]
5. PH₃, SiH₄, H₂S [19cd]
6. NHF₂, CH₂F₂, OF₂ [17c]
7. NF₃, CHF₃ [13c]
8. OF₂, OCH₃, SF₂, S(CH₃)₂ [25ab]
9. PF₃, POF₃ [21c]
10. IO₃^–, XeO₃, IO₄-, XeO₄ [27ab,77]