Q. The reactivity of an atom arises from
A) the energy differences between the electron shells
B) the existence of unpaired electrons in the valence shell
C) the average distance of the outermost electron shell from the nucleus
D) the sum of the potential energies of all the electron shells
✔ Correct Answer: the existence of unpaired electrons in the valence shell
Exam Insight
The reactivity of an atom arises from the presence of valence electrons, which determine its ability to form chemical bonds.