Proton

Proton is a subatomic particle, symbol p or p⁺, with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons".

Properties

One or more protons are present in the nucleus of every atom; they are a necessary part of the nucleus. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number. Since each element has a unique number of protons, each element has its own unique atomic number.

The word proton is Greek for "first", and this name was given to the hydrogen nucleus by Ernest Rutherford in 1920. In previous years, Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by atomic collisions. Protons were therefore a candidate to be a fundamental particle, and hence a building block of nitrogen and all other heavier atomic nuclei.

Discovery

The first use of the word "proton" in the scientific literature appeared in 1920. In the years following Rutherford's discovery, many other scientists (such as William Prout and Wilhelm Wien) attempted to prove that the hydrogen nucleus was a new, fundamental particle. It was not until the development of the quantum theory of the atom that the proton was truly accepted as a fundamental particle, and not a composite of other particles.

See also

• Neutron
• Electron
• Atomic nucleus
• Quantum mechanics

References

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  Quark structure of a proton

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  Ernest Rutherford at the 1911 Solvay Conference

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  Proton detected in an isopropanol cloud chamber

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  Hydrogen atom