An element has an atomic number of $56$. To which of the following does it belong?

The halides of alkaline earth metals form hydrates such as $MgCl_2 \cdot 6H_2O$,$CaCl_2 \cdot 6H_2O$,$BaCl_2 \cdot 2H_2O$,and $SrCl_2 \cdot 2H_2O$. What does this indicate about the halides of group $2$ elements?

Reaction of $BeO$ with ammonia and hydrogen fluoride gives '$A$' which on thermal decomposition gives $BeF_2$ and $NH_4F$. What is '$A$'?

Which one of the following is the strongest base?

Which pair of metals is present in dolomite?

Which of the following is an amphoteric hydroxide?