* One proton: Located in the nucleus, the proton carries a positive charge and contributes to the atom's mass.

* One electron: Orbiting the nucleus, the electron carries a negative charge and is much lighter than the proton.

* No neutrons: Unlike heavier atoms, hydrogen's most common isotope (protium) has no neutrons in its nucleus.

Therefore, a hydrogen atom is essentially a single proton with an electron orbiting around it.