What Makes Each Element Unique?
Just like every person has a unique identity, every element has a unique identity too — and that identity comes down to one number: the atomic number.
The atomic number (also called the proton number) is the number of protons found in the nucleus of an atom of that element. It is unique to each element and never changes.
Because atoms of the same element always have the same number of protons, the atomic number is the most fundamental way to identify an element. If you change the number of protons, you change the element entirely.
In a neutral atom, the number of electrons always equals the number of protons. So the atomic number also tells you how many electrons are orbiting the nucleus.
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