Answers

2016-01-01T08:28:37+05:30
Being favor to be in IA and VIIA groups with It's valency, It can be place over on the two groups. It may disturbs the order and properties in certain group. So, It is placed at top of the IA group but not consider as IA group element.
1 5 1
2016-01-02T10:56:40+05:30
Because it shows the characterstics of alkaline earth metals
1 5 1