Which metal in period 5 is very reactive and has two valence electrons in each atom?
rubidium (rd)
strontium (si)
zirconium (z1)
silver (ag)

The right answer is A, that is Rubidium (Rb)

Explanation:

Strontium has 2 electrons in the valance shell and is alkaline earth metal but relatively reactive.

Rubidium comes in period 5 and under alkali metals and very reactive towards oxygen and highly reactive than strontium  and other option

This element has 2 electrons in its valence subshell (5s) according to Madelung rule.

Madelung rule that if the two orbitals have the same n+l value they fill in increasing order of n.

So the right answer is A, that is Rubidium (Rb)

catya your not at all which answer i've seen you do this on another question!

a is the correct answer