Concept:The nucleus contains an atom's protons and neutrons.
Explanation:The hydrogen atom is the simplest atom.
Its atomic number is
1, meaning it has one proton in its nucleus.
The most common isotope, protium, has no neutrons.
The atom's single electron is located outside the nucleus.
An electron is negatively charged and orbits in the electron shell, so it cannot be part of the nucleus.
The proton is the only particle found inside the ordinary hydrogen nucleus.
Thus, the nucleus of a hydrogen atom consists of exactly one proton only.
Answer:A. one proton only