What is atomic number?

The atomic number is the number of protons present in the nucleus of an atom.

• Symbol: Z
• Uniquely identifies every element no two elements share the same atomic number.
• In a neutral atom, atomic number also equals the number of electrons.
• Example: Carbon has Z = 6 → 6 protons and 6 electrons.

Atomic number equals the number of protons in a nucleus and uniquely identifies every element on the periodic table.