Oxides of Group 1 elements

When cut by a knife, the exposed surface of an alkali metal or alkaline earth metal quickly turns into an oxide. These elements do not occur in nature as free metals. Instead, they react with many other elements to form white or grey water-soluble salts. With some exceptions, the oxides of group 1 elements have the formula M2O, their hydrides are MH, and their halides are MX (for example, NaCI). The oxides of group 2 elements have the formula MO, their hydrides are MH2, and their halides are MX2, for example, CaCh. 

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