What are oxides?
If you are not into chemistry at school, you can hardly remember what oxides are and what their role in the environment is. In fact, it is a fairly common type of compound that is most commonly found in the environment in the form of water, rust, carbon dioxide and sand. Oxides also include minerals - a type of rock that has a crystalline structure.
Oxides are chemical compounds whose formula contains at least one oxygen atom and atoms of other chemical elements. Metal oxides, as a rule, contain oxygen anions in oxidation state -2. A significant part of the Earth's crust consists of solid oxides, which arose in the process of oxidation of elements with oxygen from air or water. In the process of burning a hydrocarbon, two main carbon oxides are formed: carbon monoxide (carbon monoxide, CO) and carbon dioxide (carbon dioxide, CO2).
All oxides can be divided into two large groups:
- salt-forming oxides;
- non-forming oxides.
Salt-forming oxides are chemical substances, which in addition to oxygen contain elements of metals and non-metals,which form acids upon contact with water, and combining with bases - salts.
Salt-forming oxides, in turn, are divided into:
- basic oxides, in which, during oxidation, the second element (1, 2 and sometimes 3-valent metal) becomes a cation (Li2O, Na2O, K2O, CuO, Ag2O, MgO, CaO, SrO, BaO, HgO, MnO, CrO, NiO, Fr2O, Cs2O, Rb2O, FeO);
- acidic oxides, in which, when salt forms, the second element joins a negatively charged oxygen atom (CO2SO2SO3SiO2, P2O5, CrO3, Mn2O7, NO2Cl2O5Cl2O3);
- amphoteric oxides in which the second element (3 and 4-valent metals or exceptions such as zinc oxide, beryllium oxide, tin oxide and lead oxide) can become both a cation and adhere to an anion (ZnO, Cr2O3Al2O3SnO SnO2PbO PbO2, Tio2, MnO2Fe2O3BeO).
Non-forming oxides show neither acidic, nor basic, nor amphoteric properties and, as the name implies, do not form salts (CO, NO, NO2(FeFe2) O4).
- Oxygen atoms in oxides have high chemical activity. Due to the fact that the oxygen atom is always negatively charged, it forms stable chemical bonds with almost all elements, which causes a wide variety of oxides.
- Precious metals such as gold and platinum are valued becausethat they do not oxidize naturally. Corrosion of metals is formed by hydrolysis or oxidation by oxygen. The combination of water and oxygen only accelerates the reaction rate.
- In the presence of water and oxygen (or just air), the oxidation reaction of some elements, for example, sodium, occurs rapidly and can be dangerous for humans.
- Oxides create a protective oxide film on the surface. As an example, aluminum foil can be cited, which, due to the coating of a thin film of aluminum oxide, corrodes much more slowly.
- The oxides of most metals have a polymer structure, so that they are not destroyed by the action of solvents.
- Oxides dissolve under the action of acids and bases. Oxides that can react with both acids and bases are called amphoteric. Metals, as a rule, form basic oxides, non-metals - acid oxides, and amphoteric oxides are obtained from alkali metals (metalloids).
- The amount of metal oxide can be reduced by the action of some organic compounds. Such redox reactions underlie many important chemical transformations,such as detoxification of drugs under the influence of P450 enzymes and the production of ethylene oxide, which then produce antifreeze.
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