What Is the Electron Affinity?
Electron affinity is also called electron affinity, which is the energy of the affinity between electrons. Electron affinity is the energy released by a gaseous atom in the ground state to get an electron into a gaseous anion. The unit is kJ / mol (SI unit is J / mol).
- The energy released when a ground-state gaseous atom of an element gets an electron to form a -1 valence gaseous anion is called the element's first electron affinity, and it is represented by E1. One more electron is obtained from the -1-valent gaseous anion, and the energy released by the -1-valent gaseous anion is called the second electron affinity E2, and so on. The first affinity of most elemental atoms is negative, and a few are positive. [1]
- Obviously, the electron affinity of an element can reflect the ease with which an atom of the element can obtain an electron. The smaller the algebraic value of the first electron affinity of the element atom, the greater the tendency of the element atom to obtain an electron, and the stronger the non-metallicity of the element.
- In general, the algebraic value of the electron affinity decreases with increasing atomic radius, that is, decreases from top to bottom in the same family, and increases from left to right in the same period. However, it should be noted that the largest absolute value of VIA and VIIA electron affinity is not the first element of each family, but the second element. This anomaly can be explained as: the atomic radius of oxygen and fluorine in the second cycle is small, the electron density is large, and the repulsive force between electrons is strong, so that when an atom combines one electron to form a negative ion, the energy released is small, The second elements, sulfur and chlorine, have larger radii, and there are empty d orbitals in the same layer that can hold electrons. The repulsive force of the electrons is small, so the energy released when forming negative ions is the largest. [3]
- The following is the electronic affinity data of the elements, for reference only. [3]
- The definition of electron affinity can also be extended to molecules. For example, the electron affinity energy of benzene and naphthalene is negative, while the electron affinity energy of anthracene, phenanthrene and pyrene is positive. Computer simulation experiments confirmed that the electron affinity of hexacyanobenzene C6 (CN) 6 is higher than that of fullerene. [3]
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