What are protons made of?

Protons are made of quarks. A single proton consists of 3 quarks – 2 up quarks and 1 down quark.

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Protons were at one time thought to be fundamental particles, but in the second half of the twentieth century it was discovered that they are not, and that they are made of even smaller particles, known as quarks.

There are six types of quark: the up quark, the down quark, the charm quark, the strange quark, the top quark, and the bottom quark. A proton consists of just the first two: the up and the down quark.

A proton consists of three quarks – two up quarks and one down quark. All quarks have fractional electric charge. The up quark has a relative electric charge of +⅔, and the down quark has a relative electric charge of −⅓. This means that, overall, the proton has a relative electric charge of +1.