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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.
The electron affinity of molecules is a complicated function of their electronic structure. For instance the electron affinity for benzene is negative, as is that of naphthalene, while those of anthracene, phenanthrene and pyrene are positive. In silico experiments show that the electron affinity of hexacyanobenzene surpasses that of fullerene. [5]
Zinc compounds are chemical compounds containing the element zinc which is a member of the group 12 of the periodic table. The oxidation state of zinc in most compounds is the group oxidation state of +2. Zinc may be classified as a post-transition main group element with zinc(II). Zinc compounds are noteworthy for their nondescript appearance ...
Zinc oxide is generally recognized by the FDA as safe and effective [187] and is considered a very photo-stable. [188] Zinc oxide is one of the most common active ingredients formulated into a sunscreen to mitigate sunburn. [75] Applied thinly to a baby's diaper area with each diaper change, it can protect against diaper rash. [75]
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,
See also: Electronegativities of the elements (data page) There are no reliable sources for Pm, Eu and Yb other than the range of 1.1–1.2; see Pauling, Linus (1960).
Calcium hydroxide, Ca(OH) 2, is a strong base, though not as strong as the hydroxides of strontium, barium or the alkali metals. [17] All four dihalides of calcium are known. [18] Calcium carbonate (CaCO 3) and calcium sulfate (CaSO 4) are particularly abundant minerals. [19]
Zinc sulfate is an inorganic compound with the formula ZnSO 4.It forms hydrates ZnSO 4 ·nH 2 O, where n can range from 0 to 7. All are colorless solids. The most common form includes water of crystallization as the heptahydrate, [4] with the formula Zn SO 4 ·7H 2 O.