The particle with a positive charge found in the nucleus is the proton.
A proton carries one elementary positive charge, while an electron carries an equal-magnitude negative charge. Protons reside in the nucleus alongside neutrons, and the number of protons determines which chemical element an atom is. For example, every carbon atom has six protons, whereas oxygen has eight.
The proton is not an indivisible elementary particle. It is a composite hadron made of three valence quarks: two up quarks and one down quark, held together by the strong interaction and a field of gluons. Most of its mass comes from the energy of this internal strong-force system rather than simply from the quark rest masses.
The proton was identified as a distinct nuclear constituent through experiments associated with Ernest Rutherford, who reported evidence for the hydrogen nucleus in 1917. A positron is also positively charged, but it is the electron's antimatter partner and is not the ordinary nuclear particle described here.