Definition:Bohr Radius

Physical Constant
The Bohr radius $a_0$ is approximately equal to the most probable distance between the nucleus and the electron in a hydrogen atom in its ground state.

where:
 * $\varepsilon_0$ denotes the vacuum permittivity
 * $h$ denotes Planck's constant
 * $\hbar$ denotes the reduced Planck constant
 * $m_\E$ denotes the electron rest mass
 * $\E$ denotes the elementary charge
 * $c$ denotes the speed of light.
 * $\alpha$ denotes the fine-structure constant.

Also see

 * Definition:Bohr Model