The atomic number of an atom is defined as the number of protons in its nucleus. This number uniquely identifies the element and is denoted by the symbol ZZZ
. For example, hydrogen has an atomic number of 1 (one proton), carbon has an atomic number of 6 (six protons), and iron has an atomic number of 26 (twenty- six protons)
. In a neutral atom, the atomic number also equals the number of electrons
. The atomic number is always listed with the element on the periodic table, usually above the element symbol
. Key points:
- The atomic number (ZZZ) = number of protons in the nucleus
- Each element has a unique atomic number.
- In a neutral atom, atomic number = number of electrons
For example:
- Hydrogen (HHH): atomic number = 1 (1 proton)
- Carbon (CCC): atomic number = 6 (6 protons)
- Iron (FeFeFe): atomic number = 26 (26 protons)
