Which element is classified as an alkali metal? rb sr zr cl

Rb

Explanation:

Alkali metals are the most reactive metals, they do not occur freely in nature due to this high reactivity.

They are characterized by having only one electron in their valence shell which they usually use during chemical reactions to form ionic bonds.

Alkali metals occupy group 1 in the periodic table.

Checking the attached periodic table, we can conclude that alkali metals are:

Lithium (Li) , Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr)

Comparing these elements with the given choices, we will find that the correct answer is Rb.

Hope this helps :)