點解calcium唔係group1 metal，但react with water會give out hydrogen?

Except beryllium, all other Group II metal can react with water to give off hydrogen.

Magnesium reacts with cold water very slowly.
Mg(s) + 2H2O(l) → Mg(OH)2 + H2(g)
But magnesium reacts with steam vigorously.
Mg(s) + H2O(l) → MgO*s) + H2(g)

Calcium reacts with cold water steadily.
Ca(s) + 2H2O(l) → Ca(OH)2 + H2(g)

Strontium reacts with cold water vigorously.
Sr(s) + 2H2O(l) → Sr(OH)2 + H2(g)

Barium reacts with cold water more vigorously than strontium.
Ba(s) + 2H2O(l) → Ba(OH)2 + H2(g)

why calcium isnt in the group 1 metal?? coz calcium have 2 electron(e-) in there outermost shell eg Na have 1 e- in there outermost shell therefore they in group 1!!
但係react with water都會give out hydrogen gas?coz most all group1 and 2 metal is very unstatble they react with water so people usually kept them in oil!! and calcium give out hydrogen gas because of that reaction
Ca + 2H2O ------> Ca(OH)2 + H2

2006-12-18 05:36:57 補充：
is unstable not unstatble

calcium 係 第2簇，鹼土金屬,和水反應都有氫生成!

H2係由水果度出泥,唔關個metal事
Ca + H2O → CaO + H2