Question

which is the most reactive solid element?​

Answer 1

Answer:

Caesium and fluorine

Explanation:

Caesium and fluorine. Group I metals are the most reactive metals as they only have one electron in their outer shell which is easy to lose; they get more reactive as you go down the periodic table as the electron is further from the nucleus and shielded by the inner electrons. The halogens are the most reactive non-metals for the opposite reason - they only need one electron to fill their outer shell, and that is easiest for fluorine as it is the smallest and thus the incoming electron sees more of the nuclear charge.

Francium is probably more reactive than caesium, but with a half-life of 22 minutes, we can't get enough to test.