The alkaline earth metal with the lowest density is

Which of the following alkaline earth metals is the strongest reducing agent?

What is the difference in the number of water molecules between gypsum and plaster of Paris?

$Mg(NO_3)_2 \cdot XH_2O$ and $Ba(NO_3)_2 \cdot YH_2O$ represent the formulas of the crystalline forms of nitrate salts. The sum of $X$ and $Y$ is $.........$.

The solubility of carbonates of the alkaline earth metals decreases down the group. This is due to a decrease in which of the following?

Which of the following sets represents the alkaline earth metals?