What characteristic of an atom determines its properties

a. arrangement of protons in the nucleus
b. the arrangement of electrons around the nucleus
c. the atomic number of neutrons
d. the atomic mass

The correct answer to this question is actually letter B. To expound on this, let's discuss each choice.

A. The particles inside the nucleus, protons and nucleus, don't actually dictate the properties of substances because the nucleus constitutes very little space compared to the rest of the atoms.

B. It is the electrons, especially the valence electrons, that dictate the property because these are the electrons that take part in chemical reactions.

C. The atomic number is the number of protons. It has nothing to do with the neutrons.

D. The atomic mass only tells the weight of each atom. The weight does not dictate the chemical properties of a substance.