Question

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

Explanation:

Step1: Recall alkali metal group

Alkali metals are in Group 1 of the periodic table.

Step2: Analyze each option

Rb (rubidium) is in Group 1, Sr (strontium) is in Group 2, Zr (zirconium) is a transition - metal, Cl (chlorine) is a halogen.

Answer:

Rb