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In atomic physics, the Bohr model or Rutherford–Bohr model was the first successful model of the atom. Developed from 1911 to 1918 by Niels Bohr and building on Ernest Rutherford 's nuclear model , it supplanted the plum pudding model of J. J. Thomson only to be replaced by the quantum atomic model in the 1920s.
The Weiss magneton was experimentally derived in 1911 as a unit of magnetic moment equal to 1.53 × 10 −24 joules per tesla, which is about 20% of the Bohr magneton. In the summer of 1913, the values for the natural units of atomic angular momentum and magnetic moment were obtained by the Danish physicist Niels Bohr as a consequence of his ...
The electron is a charged particle with charge − e, where e is the unit of elementary charge. Its angular momentum comes from two types of rotation: spin and orbital motion. From classical electrodynamics, a rotating distribution of electric charge produces a magnetic dipole, so that it behaves like a tiny bar magnet.
For an atom with no nuclear magnetic moment, the magnitude of the atomic dipole moment, , is then [18] = (+) where j is the total angular momentum quantum number, g J is the Landé g-factor, and μ B is the Bohr magneton.
Atomic units are chosen to reflect the properties of electrons in atoms, which is particularly clear in the classical Bohr model of the hydrogen atom for the bound electron in its ground state: Mass = 1 a.u. of mass; Charge = −1 a.u. of charge; Orbital radius = 1 a.u. of length; Orbital velocity = 1 a.u. of velocity [44]: 597
The best available measurement for the value of the magnetic moment of the neutron is μ n = −1.913 042 76 (45) μ N. [3] [4] Here, μ N is the nuclear magneton, a standard unit for the magnetic moments of nuclear components, and μ B is the Bohr magneton, both being physical constants.
The Stern–Gerlach experiment was meant to test the Bohr–Sommerfeld hypothesis that the direction of the angular momentum of a silver atom is quantized. [14] The experiment was first performed with an electromagnet that allowed the non-uniform magnetic field to be turned on gradually from a null value. [1]
In the Stoner model, the spin-only magnetic moment (in Bohr magnetons) per atom in a ferromagnet is given by the difference between the number of electrons per atom in the majority spin and minority spin states. The Stoner model thus permits non-integral values for the spin-only magnetic moment per atom.