Well, the only way you would get clouds is evaporation, a liquid to a gas. (Change of matter) the clouds would not turn into rain without percipitation, gas to water. (Change of matter.)
Well, the only way you would get clouds is evaporation, a liquid to a gas. (Change of matter) the clouds would not turn into rain without percipitation, gas to water. (Change of matter.)
The answer is Strontium(Sr). The reactive increase from right to left. And this element has two valence electrons. So Rb is not correct. Then the very reactive metal is Sr.