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

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

Compare meaning

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

• proton vs. electron

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

Understanding why requires looking at the changing internal structure of a proton as its energy increases.

From Science Daily ● Aug. 16, 2026

"It's believed that the lifetime of a proton is longer than the lifespan of the universe," Lewis said.

From Science Daily ● Aug. 16, 2026

Physicists first proposed the baryon junction, also called a gluon junction, in the 1970s as a way to describe how gluons connect the valence quarks inside a proton.

From Science Daily ● Aug. 16, 2026

Understanding how proton motion influences this process could open new ways to control energy flow in advanced materials.

From Science Daily ● Jul. 22, 2026

The idea was that particles like the proton and the neutron could be regarded as waves on a string.

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

The proposed mechanism depends on what happens when protons inside colliding nuclei reach enormous energies.

From Science Daily ● Aug. 16, 2026

They also provide easier pathways for protons, oxygen, and water to move.

From Science Daily ● Aug. 8, 2026

Identifying these objects is difficult because scientists must distinguish the signals produced by protons from those created by highly energetic electrons.

From Science Daily ● Aug. 2, 2026

They also suggest that the system could identify neutrino interactions that produce final-state low-momentum protons with both high purity and high efficiency.

From Science Daily ● Jul. 17, 2026

Each of our atoms holds protons and neutrons at its center in a super-dense mass called the nucleus.

From "Meltdown" by Deirdre Langeland