How Fast Is Electron (Bohr orbit)?

An electron in a hydrogen atom's Bohr orbit moves at 2,188 km/s — 0.73% the speed of light. At this scale, classical physics fails; quantum mechanics fully takes over, and the electron has no definite position, only a probability cloud.

Electrons are point-like — they have no measurable size. Even the most precise experiments place an upper limit at about 10⁻²² metres, smaller than anything else we can measure.

• 0.73% of light speed
• At this scale, quantum mechanics rules