$X$-ray tube windows are made using which of the following metals?

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

The alkaline earth metals,which do not impart any colour to Bunsen flame are

Match List-$I$ with List-$II$ for the compositions of substances and select the correct answer using the code given below the lists.

List-$I$ Substances	List-$II$ Composition
$A$. Plaster of paris	$i$. $CaSO_4.2H_2O$
$B$. Epsomite	$ii$. $CaSO_4.\frac{1}{2}H_2O$
$C$. Kieserite	$iii$. $MgSO_4.7H_2O$
$D$. Gypsum	$iv$. $MgSO_4.H_2O$
	$v$. $CaSO_4$

Correct order of density in $IIA$ group (alkaline earth metals) is:

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 $SrCl_2 \cdot 2H_2O$. This indicates that the halides of group $2$ elements are: