Scientists Say: Atomic number

This number gives an element its place in the periodic table


This hunk of copper is element 29 on the periodic table of elements. The number refers to how many protons found in each atom of copper.


Atomic number (noun, “ah-TOM-ick number”)

This is the number of protons — positively charged particles — in a single atom. The atomic number identifies an atom as a specific element. Any atom of gold will have 79 protons, for instance. An atom with one more proton is no longer gold. It’s mercury. One less, and it’s platinum. Atomic number also determines the element’s location on the periodic table. Number one is hydrogen.

In a sentence

Scientists made four new elements by slamming smaller atoms together until their protons stuck, creating elements with the atomic numbers 113, 115, 117 and 118.

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Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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