Bohr radius

Bohr radius
Symbol	a0 or rBohr
Named after	Niels Bohr
Approximate values (to three significant digits)
SI units	5.29×10−11 m (52.9 pm)

The Bohr radius ( $a_{0}$ ) is a physical constant, approximately equal to the most probable distance between the nucleus and the electron in a hydrogen atom in its ground state. It is named after Niels Bohr, due to its role in the Bohr model of an atom. Its value is 5.29177210903(80)×10⁻¹¹ m.^[1]^[2]

^ "2018 CODATA Value: Bohr radius". The NIST Reference on Constants, Units, and Uncertainty. NIST. 20 May 2019. Retrieved 2019-05-20.
^ The number in parentheses denotes the uncertainty of the last digits.

Approximate values (to three significant digits)
Symbol	$a 0$ or $r Bohr$
Named after	Niels Bohr
SI units	5.29×10⁻¹¹ m (52.9 pm)