atomic number

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noun

the number of positive charges or protons in the nucleus of an atom of a given element, and therefore also the number of electrons normally surrounding the nucleus. Abbreviation: at. no.; Symbol: Z

Nearby words

atomic force microscope, atomic heat, atomic hydrogen, atomic mass, atomic mass unit, atomic number, atomic orbital, atomic pile, atomic power, atomic reactor, atomic spectrum

Origin of atomic number

First recorded in 1815–25

Also called proton number.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for atomic number

atomic number

noun

the number of protons in the nucleus of an atom of an elementAbbreviation: at. no. Symbol: Z Also called: proton number

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for atomic number

atomic number

n.

The number of protons in an atomic nucleus; it indicates the position of an element in the periodic table.

Science definitions for atomic number

atomic number

The number of protons in the nucleus of an atom. In electrically neutral atoms, this number is also equal to the number of electrons orbiting about the atom's nucleus. The atomic number of an element determines its position in the Periodic Table, and is usually denoted by the letter Z and written as a subscript before an element's symbol, as in 92U.

Culture definitions for atomic number

atomic number

The number of protons or electrons normally found in an atom of a given chemical element. The higher the atomic number, the heavier the atom is. In a neutral atom, the number of protons and electrons is the same. (See atomic weight and periodic table of the elements.)