Editing Bohr radius (section)

{{Short description|Unit of length about the size of a hydrogen atom}}
{{More citations needed|date=May 2025}}
{{Infobox
| title            = Bohr radius
| labelstyle       = font-weight:normal
| label1           = Symbol
| data1            = {{math|''a''<sub>0</sub>}} or {{math|''r''<sub><small>Bohr</small></sub>}}
| label2           = Named after
| data2            = [[Niels Bohr]]
| header3          = Approximate values (to three significant digits)<!--This section lists various values for c, to three significant digits. Please do not change to more exact values!-->
| label4           = [[SI units]]
| data4            = {{val|5.29|e=-11|ul=m}} ({{val|52.9|ul=pm}})
}}

The '''Bohr radius''' ({{tmath|a_0}}) is a [[physical constant]], approximately equal to the most probable distance between the [[Atomic nucleus|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 {{physconst|a0|after=.}}<ref name="uncert">The number in parentheses denotes the [[Standard deviation|uncertainty]] of the last digits.</ref>