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These tables list values of molar ionization energies, measured in kJ⋅mol −1. This is the energy per mole necessary to remove electrons from gaseous atoms or atomic ions. The first molar ionization energy applies to the neutral atoms.
The first of these quantities is used in atomic physics, the second in chemistry, but both refer to the same basic property of the element. To convert from "value of ionization energy" to the corresponding "value of molar ionization energy", the conversion is: 1 eV = 96.48534 kJ/mol 1 kJ/mol = 0.0103642688 eV [12]
For example, heats of fusion and vaporization are usually of the order of 10 kJ·mol −1, bond energies are of the order of 100 kJ·mol −1, and ionization energies of the order of 1000 kJ·mol −1. [5] For this reason, it is common within the field of chemistry to quantify the enthalpy of reaction in units of kJ·mol −1. [6]
1.7×10 −21 J 1 kJ/mol, converted to energy per molecule [9] 2.1×10 −21 J Thermal energy in each degree of freedom of a molecule at 25 °C (kT/2) (0.01 eV) [10] 2.856×10 −21 J By Landauer's principle, the minimum amount of energy required at 25 °C to change one bit of information 3–7×10 −21 J
The strength of a bond can be estimated by comparing the atomic radii of the atoms that form the bond to the length of bond itself. For example, the atomic radius of boron is estimated at 85 pm, [10] while the length of the B–B bond in B 2 Cl 4 is 175 pm. [11] Dividing the length of this bond by the sum of each boron atom's radius gives a ratio of
In the Arrhenius model of reaction rates, activation energy is the minimum amount of energy that must be available to reactants for a chemical reaction to occur. [1] The activation energy ( E a ) of a reaction is measured in kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol). [ 2 ]
, , and are the usual agents of a chemical equation with coefficients and is a positive or negative numerical value, which generally has units of kJ/mol. Another equation may include the symbol E {\displaystyle E} to denote energy; E {\displaystyle E} 's position determines whether the reaction is considered endothermic (energy-absorbing) or ...
Theoretical chemistry requires quantities from core physics, such as time, volume, temperature, and pressure.But the highly quantitative nature of physical chemistry, in a more specialized way than core physics, uses molar amounts of substance rather than simply counting numbers; this leads to the specialized definitions in this article.