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)

whats the meaning of /

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.