The atomic number of an element is the number of ______​ in the nucleus.

A) ​quarks
B) ​neutrons
C) ​protons
D) ​electrons

Atomic Number

The atomic number is equal to the number of protons (positively charged particles) in the nucleus of an atom.

Element

A pure chemical substance consisting of one type of atom distinguished by its atomic number.

Nucleus

The central and most important part of an atom, containing protons and neutrons and almost all of its mass.