Search results
Results From The WOW.Com Content Network
The classical electron radius is sometimes known as the Lorentz radius or the Thomson scattering length. It is one of a trio of related scales of length, the other two being the Bohr radius a 0 {\displaystyle a_{0}} and the reduced Compton wavelength of the electron ƛ e .
Since an electron behaves as a wave, at a given velocity it has a characteristic de Broglie wavelength. This is given by λ e = h/p where h is the Planck constant and p is the momentum. [60] For the 51 GeV electron above, the wavelength is about 2.4 × 10 −17 m, small enough to explore structures well below the size of an atomic nucleus. [147]
Diagram of a helium atom, showing the electron probability density as shades of gray. The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the outermost isolated electron. Since the boundary is not a well-defined physical entity, there are various ...
Note: All measurements given are in picometers (pm). For more recent data on covalent radii see Covalent radius.Just as atomic units are given in terms of the atomic mass unit (approximately the proton mass), the physically appropriate unit of length here is the Bohr radius, which is the radius of a hydrogen atom.
Since the reduced mass of the electron–proton system is a little bit smaller than the electron mass, the "reduced" Bohr radius is slightly larger than the Bohr radius (meters). This result can be generalized to other systems, such as positronium (an electron orbiting a positron ) and muonium (an electron orbiting an anti-muon ) by using the ...
Similarly, when an electron is added to an atom, forming an anion, the added electron increases the size of the electron cloud by interelectronic repulsion. The ionic radius is not a fixed property of a given ion, but varies with coordination number , spin state and other parameters.
The radius of the proton is defined by a formula which can be calculated by quantum electrodynamics and be derived from either atomic spectroscopy or by electron–proton scattering. The formula involves a form-factor related to the two-dimensional parton diameter of the proton. [7]
Furthermore, spectroscopic measurements can be made both with regular hydrogen (consisting of a proton and an electron) or muonic hydrogen (an exotic atom consisting of a proton and a negative muon). An inconsistency between proton charge radius measurements made using different techniques [ 12 ] was known as the proton radius puzzle , but more ...