Lithium and Sodium both react strongly and quickly with cold water to produce hydroxides and hydrogen gas along with large amount of energy in the form of heat.These have a single electron in the outermost shell.They can readily exchange this electron to produce cation which causes chemical reactions which are sometimes explosive in nature.

5 3 5
please vote this as the best answer

This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
These metals are very active so that they even react vigorously with water.
They release a large amount of energy when they react with water.
So they are called as ACTIVE METALS. 
2 1 2