Electron volt definition

Einstein s hypothesis, then, led to two definite predictions. In the first place, there should be a photoelectric threshold frequencies less than a certain limit, equal to 4>/h, should be incapable of ejecting photoelectrons from a metal. This prediction proved to be verified experimentally, and with more and more accurate determinations of work function it continues to hold true. It is interesting to see where this threshold comes in the spectrum. For this purpose, it is more convenient to find the wave length X = c/v corresponding to the frequency /h. If we express in electron volts, as is commonly done, (see Eq. (1.1), Chap. IX), we have the relation... 

The free atom definition both scales were built up for isolated atoms. The electronegativity as energy per electron the given values are expressed in electron-volts. 

Mullikan has given another definition of the electronegativity of an atom X(M) = 1(7 + A), in which I is its ionization energy and A its electron affinity. In this definition x(M) has the dimension of energy expressed in electron volts. Figures 1.4 and 1.5 on page 7 show the experimental values of I and A of the elements. 

Because this definition is not dependent on an arbitrary relative seale, it has also been termed absolute electronegativity, with the units of kilojoules per mole or electron volts. If an element has low values of both El and EA, as is the ease of most metals, electronegativity is also low. 

The semiconductor has been defined in several ways. Two of the most common definitions are based on the limits of two types of measurements (a) electrical resistance with values between 10 and 10 Q cm or 10 and 10 siemens/cm and (b) the energy gap with electronic excite energy between 0 and 3 electron volts (eV). However, some exceptions to these limits do occur. The best known material for the semiconductor is silicon (Si), but many others include naturally occurring minerals such as zinc blende (ZnS), cuprite (CU2O), and galena (PbS). 

The finite-difference (FD) definition based on vertical ionization energy (IP) and electron affinity (EA) scales was added for experimental assessment (Lackner Zweig, 1983). For comparison, the softness based chemical hardness values based on sphere-charged model of Pearson was also employed (Pearson, 1997). In all cases the atomic values were computed upon hydrogen calibration to its experimental 6.45 eV value. All values are in electron-volts (Putz, 2008c). 

Electron work-functions for the listed elemental solids. Values for crystal-specific faces are also provided where available along with those for different phases. All data is in units of electron volts. For work-function definition, see Section 2222. Data compiled from the CRC Handbook of Chemistry and Physics (1985) with corroboration, adjustments, and/or additions from Hiifner (2003). Data in italics is not well substantiated. 

Sometimes bonding energies are expressed per atom or per ion. Under these circumstances, the electron volt (eV) is a conveniently small nnit of energy. It is, by definition, the energy imparted to an electron as it falls throngh an electric potential of one volt. The joule equivalent of the electron volt is as follows 1.602 X 10 J = 1 eV. 

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