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 researchers investigated how changes in a molecule's electronic structure, the arrival of a proton and shifts in the surrounding water environment are connected during this process.

From Science Daily ● Oct. 6, 2026

That makes it possible to investigate structures even smaller than a proton.

From Science Daily ● Sep. 12, 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

The result of their bombardments of boron and other light elements by alpha rays, moreover, had led them to propose that the proton was composed of a neutron and a positive electron, or positron.

From "Big Science" by Michael Hiltzik

Experiments at the LHC, followed by studies at RHIC, detected collective flow when tiny projectiles such as protons, deuterons, and helium-3 nuclei struck much larger gold or lead nuclei.

From Science Daily ● Oct. 31, 2026

Researchers at the LHC even observed comparable flow patterns in collisions between individual protons.

From Science Daily ● Oct. 31, 2026

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

From Science Daily ● Oct. 12, 2026

At the center of the study is the coordinated motion of positively charged protons and negatively charged electrons.

From Science Daily ● Oct. 6, 2026

The electromagnetic attraction between negatively charged electrons and positively charged protons in the nucleus causes the electrons to orbit the nucleus of the atom, just as gravitational attraction causes the earth to orbit the sun.

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

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