What is the formula of calcium cyanamide?

Which of the following statement$(s)$ is (are) correct?
$(i)$ $LiF$ is less soluble in water
$(ii)$ $NaCl$ is less ionic than $CsCl$
$(iii)$ Formation of alkali metal halide is an endothermic reaction

Among the hydroxides and carbonates of $IA$ and $IIA$ group elements respectively,on moving down the group,the correct solubility order is:

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A):$ Lithium salts are hydrated.
Reason $(R):$ Lithium has higher polarising power than other alkali metal group members.
In the light of the above statements,choose the most appropriate answer from the options given below:

The alkali metals dissolve in liquid $NH_3$. Which of the following statements is correct?

The solubility of $Na_2SO_4$,$BeSO_4$,$MgSO_4$ and $BaSO_4$ in water follows the order: