What does the atomic number tell you about an atomwhat two particles add up to equal the mass number?

The atomic number is the number of the protons in an atom the two particles that add up to equal the mass is the protons and neutrons

Man i dont know this answer

What are the options? physical property can be color, smell, opacity, viscosity, density, infra red spectrum, melting and boiling points, attraction and repulson to magnets, etc.