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)