Based on the reactions of water on metals, arrange the following metals in increasing order of reactivity:

Iron, sodium magnesium, zinc, calcium.

Give a reason for the following:

Though lead is above hydrogen in the activity series, it does not react with dilute hydrochloric acid or dilute sulphuric acid.

Give a reason for the following:

Potassium and sodium are not used for reaction with dilute hydrochloric acid or dilute sulphuric acid in the laboratory preparation of hydrogen.

$\mathrm{Na} + {\mathrm{H}}_2\mathrm{O} \to \_\_\_\_\_ + \_\_\_\_\_$