What Determines a atoms reactivity. A) How many protons the atom contains
B) How many energy levels the atom contains
C) Whether the atom is metal or nonmetal
D) How many valence electrons the atom contains

The number of electrons in the outermost shell of an atom determines its reactivity. Noble gases have low reactivity because they have full electron shells. Halogens are highly reactive because they readily gain an electron to fill their outermost shell

Explanation:

does that help

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.

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