10) D

Firstly, alkali metals are the elements in group 1 of the periodic table.

A – Rubidium is more reactive than the hydrogen present in the water. Therefore, hydrogen would be formed and not rubidium

B – Melting points and boiling points decrease as you move down group 1. Therefore, sodium would have a higher melting and boiling point than rubidium.

C – Reactivity increases down group 1. Therefore, rubidium would react more vigorously than sodium in water.

D – All elements of the group 1 are stored in oil so they do not react with air. Therefore, rubidium is also stored in oil.

E – Rubidium has a valency of +1 and SO4 has a valency of -2. The formula would be Rb2SO4 and not RbSO4.