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

"We have captured for the first time how electronic changes associated with proton transfer are coupled to reorganization of the surrounding solvent," said Biasin.

From Science Daily ● Oct. 6, 2026

In that picture, a proton has a baryon number of plus one, divided equally among its three main valence quarks.

From Science Daily ● Aug. 16, 2026

Determining what actually carries baryon number matters far beyond the internal structure of a proton.

From Science Daily ● Aug. 16, 2026

This is the fourth largest proton event in the past three years, and will likely continue at or above the current level for the next several weeks as we approach the solar maximum.

From "Things Not Seen" by Andrew Clements

During an electrochemical reaction, hydrogen ions, also known as protons, can be produced or consumed at the electrodes.

From Science Daily ● Oct. 12, 2026

The researchers believe this principle could reveal opportunities to improve other electrochemical processes, particularly those involving the movement of both electrons and protons.

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

Neutrinos can on rare occasion convert chlorine atoms into argon atoms, with the same total number of protons and neutrons.

From "Cosmos" by Carl Sagan

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