Q. Describe about Oxides?
As said before, oxygen reacts practically with all the elements in the periodic table, except Lighter noble gases, to form binary compounds called oxides. An element can form more than one oxide of varied compositions, depending on the method of preparation, reaction conditions, etc. The oxides can be classified on the basis of the oxidation state of oxygen in the oxide or on the basis of their chemical nature. The first classification categorises oxides into the following five categories:
i) Normal oxides contain oxygen in its normal oxidation state of -2, e.g., Mg O, O=C=O, etc.
ii) Peroxides contain the peroxide ion, o2-2 e.g., Na-0-O-Na, Ha-0-H, etc.
iii) Sub oxides involve bonds between atoms of the element in addition to bonds between the element and oxygen, e.g., O=C=C=C=O.
iv)Super oxides contain 0-2 ion and are formed by alkali metals, e.g., KO2, Cs2O, etc.
v) Mixed oxides are regarded as composed of two simpler oxides, e.g., Pb304 (2PbO . PbO)