Question

What determines the chemical properties of an element?

A.
the number and arrangement of the electrons in an atom

B.
the number of neutrons and protons in an element

C.
the arrangement of all the neutrons, protons, and electrons

D.
the atomic mass of an atom

Answer 1

There are three factors that determine the chemical properties of an element:
The number and arrangement of electrons in an atom
The number of valence electrons
The number and arrangement of electrons

So I would believe that your answer would be A.