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This simplistic model of an atom shows protons as red spheres in the central nucleus. This model is NOT to scale; to match the scale of the nucleus the electrons (yellow) should be much smaller and much further away from the nucleus.
Original artwork by Windows to the Universe staff (Randy Russell).

A proton is one of the most important types of subatomic particles. Protons combine with electrons and (usually) neutrons to make atoms.

Protons are nearly the same size as neutrons and are much larger than electrons. A proton has a mass about 1,836 times greater than the mass of an electron, but the masses of protons and neutrons differ from each other by less than one percent. A proton has a mass of 1.6726 x 10-24 grams.

Protons have a positive electrical charge, which is sometimes called the elementary charge or fundamental charge or a charge of +1. Electrons have a charge of the same strength but opposite polarity, -1. The fundamental charge has a strength of 1.602 x 10-19 coulomb.

The nucleus of an atom is a combination of roughly equal numbers of protons and neutrons held together by the strong nuclear force. Clouds of electrons orbit the nucleus, attracted by the positive charges of the protons.

Protons are baryons, a class of subatomic particles that also includes neutrons. Protons are composed of two up quarks and one down quark.

A single electron orbiting a single proton is a simple hydrogen atom, the most abundant element in the Universe. Such hydrogen atoms often have their electron stripped away in a process called ionization, which leaves a lone proton. Such lone protons, also called hydrogen ions (H+), are very common. Because of their charges, these protons can be accelerated by electrical or magnetic fields to high energies, and can thus become a dangerous form of particle radiation.

Atomic Physics and Particle Physics

Fundamental Physics relevant to Space Weather

Space Weather

A Matter of Scale - interactive showing the sizes of things, from very tiny to huge - from NSF

Last modified September 17, 2010 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA