One hydrogen atom occupies approximately 6 x 10^(-31) m^(3). Nearly all of that volume is empty space. But then the volume occupied by every atom is overwhelmingly empty space.

The hydrogen nucleus, a single proton at the center, is about 1.7 femtometers wide (1.7 x 10^(-15) m). While the spherical electron cloud surrounding it (which contain one solitary electron) has a Bohr radius of approximately 50 picometers (5 x 10^(-11) m).