the same as the atomic number. the same as the group number. the sum of protons and neutrons. the difference between protons and electrons.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: The atomic mass of an atom is
Possibilities:
- the same as the atomic number.
- the same as the group number.
- the sum of protons and neutrons.
- the difference between protons and electrons.

the sum of protons and neutrons.