Chile saltpetre is

Give two uses of caustic soda.

Give the general electronic configuration of alkali metals and provide the electronic configuration for each element of the alkali metal group.

Which of the following elements is used in a photoelectric cell?

Which of the following gives a green colour to flame?

Comment on each of the following observations:
$(a)$ The mobilities of the alkali metal ions in aqueous solution are
$Li^{+} < Na^{+} < K^{+} < Rb^{+} < Cs^{+}$
$(b)$ Lithium is the only alkali metal to form a nitride directly.
$(c)$ $E^{\circ}$ for $M^{2+}_{(aq)} + 2e^{-} \longrightarrow M_{(s)}$ (where $M = Ca, Sr$ or $Ba$) is nearly constant.