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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.
In any case, the value of the electron affinity of a solid substance is very different from the chemistry and atomic physics electron affinity value for an atom of the same substance in gas phase. For example, a silicon crystal surface has electron affinity 4.05 eV, whereas an isolated silicon atom has electron affinity 1.39 eV.
[32] [33] It is intermediate in atomic radius between chlorine and iodine, and this leads to many of its atomic properties being similarly intermediate in value between chlorine and iodine, such as first ionisation energy, electron affinity, enthalpy of dissociation of the X 2 molecule (X = Cl, Br, I), ionic radius, and X–X bond length. [31]
One can test for a bromide ion by adding an oxidizer. One method uses dilute HNO 3. Balard and Löwig's method can be used to extract bromine from seawater and certain brines. For samples testing for sufficient bromide concentration, addition of chlorine produces bromine (Br 2): [7] Cl 2 + 2 Br − → 2 Cl − + Br 2
The bromide ion acquires a positive formal charge. At this moment the halogen ion is called a "bromonium ion" or "chloronium ion", respectively. When the first bromine atom attacks the carbon–carbon π-bond, it leaves behind one of its electrons with the other bromine that it was bonded to in Br 2. That other atom is now a negative bromide ...
The energy required to remove one or more electrons to make a cation is a sum of successive ionization energies; for example, the energy needed to form Mg 2+ is the ionization energy required to remove the first electron from Mg, plus the ionization energy required to remove the second electron from Mg +. Electron affinity is defined as the ...
where I is the ionization potential and A the electron affinity. This expression implies that the chemical hardness is proportional to the band gap of a chemical system, when a gap exists. The first derivative of the energy with respect to the number of electrons is equal to the chemical potential , μ , of the system,
The electron affinity (usually given by the symbol in solid state physics) gives the energy difference between the lower edge of the conduction band and the vacuum level of the semiconductor. The band gap (usually given the symbol E g {\displaystyle E_{\rm {g}}} ) gives the energy difference between the lower edge of the conduction band and the ...