proton

/ˌproʊˈtɑn/

/ˈprʌʊtɒn/

Other forms: protons

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.

Definitions of proton

1. noun

   a stable particle with positive charge equal to the negative charge of an electron
   types:

   hydrogen ion

   a positively charged atom of hydrogen; that is to say, a normal hydrogen atomic nucleus

   type of:

   nucleon

   a constituent (proton or neutron) of an atomic nucleus