12/31/2022 0 Comments Electron affinity trend![]() ![]() Hence beryllium resists gaining extra electrons in higher energy 2p orbital. Therefore, lithium has affinity to receive electrons in 2s sub-shell but for beryllium, a still higher energy 2p level is needed. Lithium has an incompletely filled 2s subshell while beryllium has a filled subshell. The atomic number and electronic configuration lithium and beryllium are, The EA trend for period-1 and period-2 elements of the periodic table are given below the picture,Įlectron affinity exceptions Electron affinity of lithium and beryllium There are many exceptions to general periodic trends. Electron affinity periodic trendĮA values generally increase on moving left to right in a period of the periodic table. Because of a high value of electron density opposed by the interelectronic repulsion forces. These unexpected behavior explained by charge densities for the respective negative ions. But the electron affinities values of the second-period elements are smaller than the third-period elements. The elements of the second period are relatively smaller in size than the third-period elements. The magnitude of electron affinity generally decreases in the same direction. When we move down a group in the periodic table, the size of atoms generally increases with increasing atomic number. The electric polarization of hydride ions is also very high. It has a very low EA (73 kJ mol −1) due to the formation of stable alkali hydride. Hydrogen atom when gaining one electron to form H − ion. The noble gases have ns 2, np 6 valence shell configurations that possess a very low value of affinity due to stable valence shell configuration. The magnitude of EA depends on the electronic structure or configuration of an atom. Hence the magnitude of the electron affinity of periodic elements increases with the increasing effective nuclear charge of an atom. As a result, higher energy is released when extra electrons are added to an atom. The greater force of attraction is exerted by the nucleus of an atom. ![]() Higher the magnitude of effective nuclear charge (Z eff) greater the tendency to attract the additional electrons towards itself. Therefore, the electron affinities decrease with increasing the size or radius of an atom. Which decreases the force of attraction exerted by the nucleus of an atom. Larger the atomic size lesser the tendency of atoms to attract the additional electrons towards themselves. The electron affinity trend in the periodic table is influenced by the following factors, Electron affinity trend in the periodic table ![]() #ELECTRON AFFINITY TREND FREE#The free energy is calculated from the temperature dependence of the chemical equilibrium constant. This gives the standard free energy for the equilibrium reaction. The second method determined the number of neutral atoms, ions, and electrons with the mass spectrometer in the electromagnetic spectrum radiation. ![]() Affinities are also measured by direct study of electron capture from heated filaments. It is difficult to obtain but measure from the indirect measurement of Born-Haber energy cycles in which one step is electron capture reaction. Putting the values from the above table, the calculated value of E Cl = −348.6 kJ mol −1. ΔH f = U NaCl + IE Na + EA Cl + S Na + ❝ Cl The formation of sodium chloride crystal lattice from sodium and chlorine atom is given below the table, The lattice energy of sodium chlorideīorn – Haber Cycle equation for the formation of crystalline solid, sodium chloride, Indirectly, electron affinity can be calculated from Born – Haber cycle data. The periodic table trend of EA is affected mostly by the atomic size, shielding electron, and electron configuration. The above electron affinity equation is an exothermic reaction with the negative sign according to the usual thermodynamics convention in chemistry but the measurement of affinities is always the positive value.Įlectron affinity value measured by unit eV per atom or kJ mol −1. In electron affinity, the energy is released with the addition of one or more electrons in an atom or anion. In ionization energy, energy is supplied to remove one or more electrons from an atom or a cation. Electron affinity ( EA) or electron gain enthalpy or simply affinity in the periodic table defines the amount of energy released when an electron is added to an isolated neutral gaseous atom in its lowest energy level (ground state) to produce an anion. ![]()
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