proton

American  

[proh-ton] / ˈproʊ tɒn /

noun

Physics, Chemistry.

• protons
  plural

1. a positively charged elementary particle that is a fundamental constituent of all atomic nuclei. It is the lightest and most stable baryon, having a charge equal in magnitude to that of the electron, a spin of ½, and a mass of 1.673 × 10 -27 kg. P

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proton British  

/ ˈprəʊtɒn /

noun

1. a stable, positively charged elementary particle, found in atomic nuclei in numbers equal to the atomic number of the element. It is a baryon with a charge of 1.602176462 × 10 ^–19 coulomb, a rest mass of 1.672 62159 × 10 ^–27 kilogram, and spin 1/ 2

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proton Scientific  

/ prō′tŏn′ /

1. A stable subatomic particle in the baryon family having a mass of 1.672 × 10 ^{- 24} grams (1,836 times that of the electron) and a positive electric charge of approximately 1.602 × 10 ^{- 19} coulombs. Protons make up part of the nucleus of all atoms except hydrogen, whose nucleus consists of a single proton. In neutral atoms, the number of protons is the same as the number of electrons. In positively charged atoms, the number of protons is greater than the number of electrons, and in negatively charged atoms electrons outnumber protons. Protons are believed to be composed of two up quarks and one down quark.

2. See Table at subatomic particle

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proton Cultural  

1. An elementary particle with a positive charge, found in the nucleus of an atom.

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Discover More

Protons and neutrons make up most of an atom's mass.

A proton is over a thousand times heavier than an electron.

Other Word Forms

Derived Forms

• protonic
  adjective

Inflected Forms

Nouns

• protons
  plural

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Etymology

Origin of proton

Term first suggested in 1920 by English physicist Ernest Rutherford as noun use of Greek prôton, neuter of prôtos “first,” the proton being the constituent of hydrogen nuclei, and formed on the analogy of electron; see first, electron

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Compare meaning

How does proton compare to similar and commonly confused words? Explore the most common comparisons:

• proton vs. electron

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Explanation

Atoms are made up of three main particles: protons, electrons, and neutrons. A proton has a positive electrical charge, while electrons are negative. The number of protons and electrons is equal in each atom. The atomic number of an element, which is the number in the upper left corner of its box on the periodic table, is the number of protons in each atom. The hydrogen atom, for example, has just one proton, so it also has one electron and its atomic number is 1. If you have an atom with two protons in its nucleus, you know it can't be a hydrogen atom.

Example Sentences

See Examples For:

proton protons

He completed nine rounds of chemotherapy and proton beam radiation.

From BBC ● Oct. 11, 2026

The molecule absorbs light and, in acidic conditions, captures a proton from its surroundings.

From Science Daily ● Oct. 6, 2026

"X-ray scattering mostly sees atoms that are rich with electrons, and so the proton is not seen directly," she said.

From Science Daily ● Oct. 6, 2026

"While this was an experiment-driven discovery, our theoretical work provided the molecular-level interpretation needed to translate the X-ray measurements into a detailed picture of the underlying coordination between proton, electron and solvent motion."

From Science Daily ● Oct. 6, 2026

The fourth category is the strong nuclear force, which holds the quarks together in the proton and neutron, and holds the protons and neutrons together in the nucleus of an atom.

From "A Brief History of Time: And Other Essays" by Stephen Hawking

This matters because the movement of protons can change local acidity.

From Science Daily ● Oct. 12, 2026

They found that approximately 89% of the studies involved reactions at one or more electrodes in which both electrons and protons were transferred.

From Science Daily ● Oct. 12, 2026

Electrons move on extremely short timescales, and protons move nearly as fast.

From Science Daily ● Oct. 6, 2026

They are found inside particles such as protons and neutrons and are roughly a billion times smaller than an atom.

From Science Daily ● Sep. 26, 2026

The number of protons is what gives an atom its chemical identity.

From "A Short History of Nearly Everything" by Bill Bryson

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