Magnesia is

Assertion $A$: Barium is not required in the normal biochemical processes of the human body.
Reason $R$: Barium does not exhibit more than one oxidation state.

Among the following alkaline earth metal halides,the one which is covalent and soluble in organic solvents is:

$Beryllium$ and $magnesium$ do not give colour to flame whereas other alkaline earth metals do so. Why?

Bleaching powder is obtained by the reaction of chlorine gas with ........

The difference in the number of water molecules in gypsum and plaster of Paris is: