Question

the difference between an atom like ca, and an ion of an atom, like ca²⁺, is a the number of protons. b the number of neutrons. c the number of proteins. d the number of electrons.

Explanation:

An atom becomes an ion by gaining or losing electrons. The number of protons and neutrons remains the same in a neutral atom and its ion. Proteins are not related to the structure of an atom or ion. So the difference between an atom and its ion is the number of electrons.

Answer:

D. the number of electrons