atomic number

noun

Definition of atomic number

: an experimentally determined number characteristic of a chemical element that represents the number of protons in the nucleus which in a neutral atom equals the number of electrons outside the nucleus and that determines the place of the element in the periodic table — see Chemical Elements Table

Examples of atomic number in a Sentence

Recent Examples on the Web Rare earths are a group of 17 metals, classified into lights and heavies depending on their atomic number, and are crucial to the manufacturing of high-tech products. Mary Hui, Quartz, 14 May 2021 But today who needs to know the capital of South Dakota or the atomic number of hafnium (Pierre and 72)? Louis Menand, The New Yorker, 16 Nov. 2020 Naturally occurring silicon has an atomic number of 14, with 14 electrons that are arranged in valence layers of 2, 8, and 4. Caroline Delbert, Popular Mechanics, 11 Feb. 2020 Some rare earths are heavy and some are light, depending on their atomic number, and the two have different applications. Naomi Xu Elegant, Fortune, 10 Sep. 2019 How to Read the Table Many periodic tables include the atomic number (number of protons) and atomic weight (which depends on protons and neutrons). Bill Andrews, Discover Magazine, 26 June 2019 For the types of BECs that form droplets, the repulsive forces are not just a function of the density but also the atomic number. Chris Lee, Ars Technica, 28 Nov. 2018 Among the atoms resulting from neutron bombardment were much smaller atoms like barium, which has an atomic number of 56. Umair Irfan, Vox, 11 June 2018 Here are some of the basics: Uranium is the heaviest naturally occurring element in the periodic table, with an atomic number of 92, representing the number of protons in its nucleus. Umair Irfan, Vox, 11 June 2018 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'atomic number.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of atomic number

1913, in the meaning defined above

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Time Traveler for atomic number

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The first known use of atomic number was in 1913

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Dictionary Entries Near atomic number

atomic mass unit

atomic number

atomic reactor

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Cite this Entry

“Atomic number.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/atomic%20number. Accessed 3 Jul. 2022.

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More Definitions for atomic number

atomic number

noun
atomic num·​ber | \ -ˈnəm-bər How to pronounce atomic number (audio) \

Medical Definition of atomic number

: an experimentally determined number characteristic of a chemical element that represents the number of protons in the nucleus which in a neutral atom equals the number of electrons outside the nucleus and that determines the place of the element in the periodic table — see Chemical Elements Table

More from Merriam-Webster on atomic number

Britannica.com: Encyclopedia article about atomic number

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