atomic number

number of protons within a nucleus

See also: List of elements by atomic numberIn chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. It is traditionally represented by the symbol Z. The atomic number uniquely identifies a chemical element. In an atom of neutral charge, the number of electrons also equals the atomic number.
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Noun
1. the order of an element in Mendeleyev's table of the elements; equal to the number of protons in the nucleus or electrons in the neutral state of an atom of an element
(hypernym) number
(hyponym) magic number

the number of protons and electrons in an atom of a specific element in the ground state.

The number of protons in an atomic nucleus. It is usually denoted by the letter Z. See also atomic mass number.