atomic number 
noun Chemistry
The number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table. (Symbol: Z) 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.
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