Question

multiple - choice question

1. what is the atomic number equal to?

number of neutrons in the nucleus
number of protons in the nucleus
number of electrons in the nucleus

Explanation:

The atomic number of an element is defined as the number of protons in the nucleus of an atom of that element. Neutrons contribute to the mass - number, and electrons are outside the nucleus in a neutral atom.

Answer:

Number of protons in the nucleus