Oxides are complex chemicals which consist of two elements. One of them is oxygen. Oxides in most cases are acid and the main. As it is easy to understand from the name, acid oxides react with the bases, forming salt, that is, showing properties of acid. How to make formulas of oxides?
Instruction
1. Many of oxides are capable to react with water, forming acid. For example: SO3 + H2O = H2SO4 (sulfuric acid) .SiO2 + 2KOH = K2SiO3 + H2O is formed (insoluble oxide of silicon in water reacts with potassium hydroxide.
2. The main oxides, on the contrary, react with acids, also forming salt and water. The same from them which are soluble in water react with it, forming the basis. Characteristic examples: ZnO + 2HCl = ZnCl2 + H2O (insoluble oxide of zinc in water reacts with hydrochloric acid) .Na2O + H2O = 2NaOH
3. It is necessary to remember that oxygen valency in oxide always equals 2. Proceeding from it, by drawing up a formula it is necessary to know the valency of the second element only. For example: alkaline metals of the first group – monovalent. Therefore the general formula of oxides will look so: El2O. I.e., Li2O, Na2O, K2O, Rb2O. (Al – "Element").
4. Alkaline-earth metals of the second group – bivalent. The general formula of oxides – ElO. Also it will look: VeO, MgO, SaO, SrO.
5. Amphoteric elements of the third group, respectively, trivalent. The general formula of oxides – El2O3. A characteristic example – already mentioned Al2O3 aluminum oxide.
6. Elements of the fourth group show or more acid properties (carbon, silicon), or it is more than main (germaniye, tin, lead). Anyway, the general formula – ElO2 (CO2, SiO2).
7. The general formula of the fifth group – El2O5. An example – the highest nitrogen oxide, N2O5 from which receive nitric acid. Or the highest oxide of vanadium, V2O5 (though vanadium – metal, its highest oxide shows acid properties).
8. Respectively, a formula of the sixth group where there is an oxygen – ElO3. The highest oxides are SO3, CrO3, WO3. Pay attention that though chrome and tungsten – metals, their highest oxides by analogy with vanadium oxide also show acid properties.
9. It is necessary to specify that only the highest oxides of elements were specified. So, for example, besides CrO3 chrome oxide where chrome shestivalenten, is Cr2O3 oxide where this element has the valency equal 3. Besides N2O5 nitrogen oxide, there are oxides N2O, NO, NO2. There is a lot of similar examples. Therefore, when writing a formula of oxide, check what valency the element connected to oxygen has in this connection!