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Physical Properties Of Oxide

wallpapers Resource 2020-12-01
Oxides are compounds (of course they must be pure). Its composition contains only two elements, one of which must be oxygen element, if the other is a metal element, it is called a metal oxide; if the other is not a metal element, it is called a non-metal oxide.
 
Physical properties
 
Among the characteristic oxides of the elements, all the oxides of short-period elements are white, while the oxides of some elements in the long-period are colored. This is because each cation has the same 8-electron configuration, but As the positive charge increases and the radius decreases, their polarization to O(2-) ions gradually increases, making the energy difference between the excited state and the ground state smaller and smaller, so that it can absorb part of the visible light to make The electrons concentrated on the oxygen end migrate to the metal end (this electron migration is called a charge transition), and their absorption bands move to the long wave direction, causing the color of the oxide to gradually deepen.

 
In the characteristic oxides, there are Cd, Ag, In, Sb, Te in the fifth period, W, Re, Os, Hg, Tl, Pb, Bi in the sixth period, and many lanthanides and Oxides of actinides. The color of these transition element oxides is caused by charge transitions in some cases, and d-d transitions in others. In oxides of lanthanides and actinides, coloring is more common.
 
Since most metal oxides have an infinite three-dimensional ionic lattice, and some non-metal oxides have a network-like covalent structure, a considerable number of oxides are refractory substances, including BeO, MgO, CaO, Al2O3, ZrO2, HfO2 and ThO2 and SiO2 are extremely refractory, and their melting points are generally between 1800~3300K, so they are excellent high-temperature ceramic materials.
 
For those oxides that exist in molecular unit structures, most of them are molecular crystals, and covalent molecules are combined with weak van der Waals forces, so their melting and boiling points are relatively low. Among them, most are gaseous at room temperature, such as CO, CO2, N2O, NO, N2O3, NO2, N2O5, SO2 and ClO2, etc.; liquid ones include Cl2O7, Mn2O7; solid ones include RuO4 and OsO4, but they are very easy to melt. (Melting points are 298.6K and 313.8K, respectively).

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