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, that of hydrogen, a single electron orbits, and the smallest possible orbit for the electron, that with the lowest energy, is the one at a distance from the nucleus called the Bohr radius. The Bohr model of the atom In atomic physics, the Bohr model depicts the atom as a small, positively charged nucleus surrounded by electrons in orbit - similar in structure to the solar system. ... Properties For alternative meanings see atom (disambiguation). ... Niels Bohr Niels Henrik David Bohr (October 7, 1885 – November 18, 1962) was a Danish physicist who made essential contributions to understanding atomic structure and quantum mechanics. ... Link title1913 is a common year starting on Wednesday. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... Plural: nuclei In chemistry and physics, the nucleus (atomic nucleus) is the collection of protons and neutrons in the center of an atom that carries the bulk of the atoms mass and positive charge. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...

The Bohr radius has a value of 5.291772108(18)×10^-11 m (according to 2002 CODATA), i.e., approximately 53 pm or 0.53 angstroms. This value can be computed in terms of other physical constants: The metre is the basic unit of length in the International System of Units (SI: Système International dUnités). ... CODATA (Committee on Data for Science and Technology) was established in 1966 as an interdisciplinary committee of the International Council of Science (ICSU), formerly the International Council of Scientific Unions. ... Picometre (American spelling: picometer) is an SI measure of length that is equal to 10−12 of a metre. ... An angstrom or ångström (Å) is a non-SI unit of length equal to 10−10 metres, 0. ...

where:

is the permittivity of vacuum

is Dirac's constant or the "reduced Planck's constant"

m_e is the reduced mass of the electron-nucleus system, very nearly the electron rest mass

e is the elementary charge

c is the speed of light

α is the fine structure constant

The Bohr radius is often used as a unit in atomic physics, see atomic units. The permittivity of a medium is an intensive physical quantity that describes how an electric field affects and is affected by the medium. ... Plancks constant, denoted h, is a physical constant that is used to describe the sizes of quanta. ... Plancks constant, denoted h, is a physical constant that is used to describe the sizes of quanta. ... Reduced mass is a concept that allows one to solve the two-body problem of mechanics as if it were a one body problem. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... Cherenkov effect in a swimming pool nuclear reactor. ... The fine-structure constant or Sommerfeld fine-structure constant, usually denoted , is the fundamental physical constant characterizing the strength of the electromagnetic interaction. ... Atomic units (au) are a convenient system of units of measurement used in atomic physics, particularly for describing the properties of electrons. ...