Final answer:
A proton is a positively charged subatomic particle located in the nucleus of an atom with a charge of +1 and a mass of 1 amu. It determines the atomic number of an element and, together with neutrons, makes up most of the atom's mass.
Step-by-step explanation:
A proton is a subatomic particle with a positive electric charge found in the nucleus of an atom. Protons are one of the three main components of atoms, along with electrons and neutrons. Each proton has a positive electrical charge of one (+1) and a standardized mass approximately equal to 1 atomic mass unit (amu) or 1.67 × 10-27 kilograms. The number of protons in the nucleus of an atom determines the atomic number of an element, which defines its place on the periodic table and its chemical properties.
Protons are made up of smaller particles called quarks, specifically two 'up' quarks and one 'down' quark. In a neutral atom, the number of protons is equal to the number of electrons, thereby balancing the positive and negative charges and making the atom electrically neutral. Protons, along with neutrons (together referred to as nucleons), account for almost all of the mass of an atom.