The atomic number of an element represents the number of:

protons

electrons

protons and neutrons

neutrons

protons

Explanation:

By definition the atomic number of an element is the number of protons.

The protons are the positevely charged particles in the nucleus of the atom.

The atomic number of an element is what uniquely identifies it. There are 118 known elements and all of them are represented in the periodic table. Then, there are 118 different atomic numbers.

The elements are arranged in the periodic table in increasing order ot atomic number.

For instance:

The element with atomic number 1 is hydrogen (H). It is the first element in the periodic table, located in the upper left corner of the table. It has one proton. NONE other element has just one proton.

The element with atomic number 2 is helium (He). It has two protons, is located at the upper right corner of the periodic table and NONE other element has just two protons.

The element with atomic number 118 is Oganesson (Og). It is the last element in the periodic table. It is located in the bottom right corner of the periodic table. It has 118 protons and NONE other element has atomic number 118.