Definition of atomic number in English:

atomic number

(also Z)


  • The number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.

    • ‘In those cases in which the number of protons changes, the new nucleus has a different atomic number, and it therefore belongs to a different element.’
    • ‘In a neutral atom, the number of electrons is equal to the number of protons, therefore, the atomic number also indicates the number of electrons in an atom.’
    • ‘We now have data on the properties of 29 new nuclei with atomic numbers between 104 and 118.’
    • ‘There, elements are arranged according to their atomic number - the number of protons in the nuclei.’
    • ‘When you move down the periodic table, as the atomic numbers increase, the elements become rarer.’
    • ‘The higher the atomic number, the more shells and electrons an atom will have.’
    • ‘The existence of an element with an atomic number of 21 was predicted in 1869 by Dmitri Mendeleev.’
    • ‘Heavy metals are metallic elements that have a high atomic number and are poisonous to living organisms.’


atomic number

/əˈtɑmɪk ˈnəmbər/