Out of the following elements,which one do you expect to be most reactive chemically?

Property of the alkaline earth metals that increases with their atomic number is

Gypsum is added into the Portland Cement to:

Which of the following is the characteristic outer shell electronic configuration of alkaline earth metals?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Barium carbonate is insoluble in water and is highly stable.
Reason $R$: The thermal stability of the carbonates increases with increasing cationic size.
Choose the most appropriate answer from the options given below for $A$ and $R$.

Which of the following statements is true regarding alkaline earth metals?