PLEASE HELP, I WILL MARK BRAINIEST what determines an atom's reactivity?

#1. how many protons the atom contains
#2. how many energy levels the atom contains
#3. whether the atom is a metal or a non-metal
#4. how many valence electrons the atom contains

D) How many valence electrons the atom contains.

Explanation:

This is the only closest one

because the number of electrons in the outermost shell is the correct answer

his research revealed two genetically different groups of prokaryotes, which justified splitting kingdom monera into two kingdoms. the genetic and cellular differences were so great, that these two kingdoms were eventually placed into different domains in the current three-domain system.

correct answer is option a.

tropopause, stratopause and mesopause have all in common aspect that is point of maximum temperature in its layer of the atmosphere. all layers of atmosphere observe abrupt change in temperature. tropopause is the boundary between troposphere and stratosphere. stratopause is the boundary between stratosphere and mesosphere. mesopause is the boundary between mesosphere and thermosphere. these all boundaries are ranges between altitude of 0 to 80 km.