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Electron affinity can be defined in two equivalent ways. First, as the energy that is released by adding an electron to an isolated gaseous atom. The second (reverse) definition is that electron affinity is the energy required to remove an electron from a singly charged gaseous negative ion.
Electron capture for almost all non-noble gas atoms involves the release of energy [4] and thus is exothermic. The positive values that are listed in tables of E ea are amounts or magnitudes. It is the word "released" within the definition "energy released" that supplies the negative sign to ΔE.
The bond dissociation energy (enthalpy) [4] is also referred to as bond disruption energy, bond energy, bond strength, or binding energy (abbreviation: BDE, BE, or D). It is defined as the standard enthalpy change of the following fission: R—X → R + X. The BDE, denoted by Dº(R—X), is usually derived by the thermochemical equation,
where is some thermodynamic property at given temperature, volume and mole numbers, is value of the property for an ideal gas, and is the residual property. The reference state is typically incorporated into the ideal gas contribution to the value, as
For example, an electron and a positron, each with a mass of 0.511 MeV/c 2, can annihilate to yield 1.022 MeV of energy. A proton has a mass of 0.938 GeV/c 2. In general, the masses of all hadrons are of the order of 1 GeV/c 2, which makes the GeV/c 2 a convenient unit of mass for particle physics: [4]
In electrochemistry, the Nernst equation is a chemical thermodynamical relationship that permits the calculation of the reduction potential of a reaction (half-cell or full cell reaction) from the standard electrode potential, absolute temperature, the number of electrons involved in the redox reaction, and activities (often approximated by concentrations) of the chemical species undergoing ...
Electron binding energy, more commonly known as ionization energy, [3] is a measure of the energy required to free an electron from its atomic orbital or from a solid. The electron binding energy derives from the electromagnetic interaction of the electron with the nucleus and the other electrons of the atom, molecule or solid and is mediated ...
Activation energy can be thought of as the magnitude of the potential barrier (sometimes called the energy barrier) separating minima of the potential energy surface pertaining to the initial and final thermodynamic state. For a chemical reaction to proceed at a reasonable rate, the temperature of the system should be high enough such that ...