Throughout the development of particle physics, scientists have created different models to understand the atom. When we are talking about the diameter of an atom, we would refer to the Bohr radius, which is the radius from the nucleus to the orbiting electron.
In this case, a hydrogen atom has one electron, and the Bohr radius in the ground state is 5.29 x 10^{-11} meters. To find the diameter, we just multiply the Bohr radius by 2.
diameter = 2 x 5.29 x 10^{-11} meters
diameter = 10.58 x 10^{-11} meters
diameter = 1.058 x 10^{-10} meters
The diameter of a hydrogen atom in ground state is:
1.058 x 10^{-10} meters