White metal is an alloy of

Which elements of group $1$ and $2$ differ from the other elements of the same group? Give a brief explanation of the diagonal relationship.

Match List-$I$ with List-$II$:

List-$I$	List-$II$
$(a)$ $Li$	$(i)$ photoelectric cell
$(b)$ $Na$	$(ii)$ absorbent of $CO_{2}$
$(c)$ $K$	$(iii)$ coolant in fast breeder nuclear reactor
$(d)$ $Cs$	$(iv)$ treatment of cancer
	$(v)$ bearings for motor engines

Choose the correct answer from the options given below:

Which among the following elements is used in devising photoelectric cells?

Which among the following is used in the breathing equipment for mountaineers?

The reason why alkali metals impart color to the Bunsen burner flame is ......