Final answer:
Protons are subatomic particles situated in the nucleus of an atom which determine the element's identity. They have a positive charge and, along with neutrons, account for most of the atom's mass. The exact arrangement of protons was deduced from Ernest Rutherford's groundbreaking experiments.
Step-by-step explanation:
Protons are subatomic particles found within the atomic nucleus. They possess a positive electrical charge of one (+1) and have a significant mass of approximately 1 atomic mass unit (amu), which is roughly 1.67 × 10-27 kilograms. The number of protons in an atom's nucleus determines the chemical element of the atom. In concert with neutrons, protons contribute almost all of the mass of an atom. Electrons, which carry a negative charge, orbit the nucleus in a region known as the electron cloud.
In atomic theory, protons and neutrons make up the very small and dense nucleus at the center of the atom. This nucleus carries a positive charge due to the protons. In a neutral atom, there are as many electrons—with a negative charge—as there are protons, balancing the atom's overall charge.
Historical experiments by Ernest Rutherford were crucial in revealing this nuclear structure of atoms, placing both protons and neutrons in the central nucleus with electrons in orbit around it. Therefore, protons, along with neutrons, are located in the nucleus of the atom.