Chemists assign atoms to chemical elements by counting their

Explanation:

There are 118 different known elements.

Each element is identified by the number of protons and it is called the atomic number. For instance, the atomic number of hydrogen is 1, every hydrogen atom has one proton; the atomic number of oxygen is 8, every oxygen atom has 8 protons; the atomic number of carbon is 6, every carbon atom has 6 protons.

There are not two different elements with the same atomic number (number of protons).

The 118 known elements are listed in the periodict table in groups (columns) and periods (rows) in increasing order of atomic number (number of protons).

So, by counting the number of protons of an atom, chemists can tell the element to which the atom belong.