The atomic number of an element represents the number of protons in the nucleus of each atom of that element. It uniquely identifies the element because every atom of a given element has the same number of protons
. In a neutral (non-ionized) atom, the atomic number also equals the number of electrons orbiting the nucleus, balancing the positive charge of the protons with an equal negative charge from the electrons
. Thus, the atomic number:
- Defines the chemical identity of an element (e.g., atomic number 8 means oxygen)
- Equals the number of protons in the nucleus
- Equals the number of electrons in a neutral atom
The atomic number is symbolized by ZZZ and is used to arrange elements in the periodic table in order of increasing ZZZ
. In summary, the atomic number represents the number of protons in an atom's nucleus and determines the element's identity and its position in the periodic table.
