Bohr radius
| Bohr radius | |
|---|---|
| Unit of | length |
| Symbol | a0 or rBohr |
| Named after | Niels Bohr |
| 1 a0 in ... | ... is equal to ... |
| SI units | 5.29×10−11 m |
| imperial/US units | 2.08×10−9 in |
| natural units |
2.68×10−4/eV 3.27×1024 ℓP |
The Bohr radius (a0 or rBohr) is a physical constant, approximately equal to the most probable distance between the center of a nuclide 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 5.2917721067(12)×10−11 m
In SI units the Bohr radius is:
where:
In Gaussian units the Bohr radius is simply
According to 2014 CODATA the Bohr radius has a value of 5.2917721067(12)×10−11 m (i.e., approximately 53 pm or 0.53 angstroms).
In the Bohr model of the structure of an atom, put forward by Niels Bohr in 1913, electrons orbit a central nucleus. The model says that the electrons orbit only at certain distances from the nucleus, depending on their energy. In the simplest atom, hydrogen, a single electron orbits the nucleus and its smallest possible orbit, with lowest energy, has an orbital radius almost equal to the Bohr radius. (It is not exactly the Bohr radius due to the reduced mass effect. They differ by about 0.1%.)
Although the Bohr model is no longer in use, the Bohr radius remains very useful in atomic physics calculations, due in part to its simple relationship with other fundamental constants. (This is why it is defined using the true electron mass rather than the reduced mass, as mentioned above.) For example, it is the unit of length in atomic units.
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