What kind of group 1 atoms are the most reactive?

a. Small atoms

c. Atoms with the most electrons in the valence level

b. Large atoms

d. Atoms at the top of the periodic table

Answer: - B, Large atoms.

Explanations: - An element is highly reactive if it could easily loses electron from it's outer most shell.

It's easy for an atom to lose the electron from it's outer most shell if it's size is bigger means the electron is farther from the nucleus. The distance of an electron from it's nucleus increases as we move down in a group as the new shells are being added.

So, the elements become larger as we move down in a group and so it's easy for them to lose the electron from their outer most shell and so they are move reactive.

For example, K is more reactive than Na as K is below Na in the periodic table.