Skill 7.6 Predicting physical and chemical properties based on the bonding in a substance

Skill 7.6 Predicting physical and chemical properties based on the bonding in a substance 

Much of chemistry consists of atoms bonding to achieve stable valence electron configurations. Nonmetals gain electrons or share electrons to achieve these configurations and metals lose electrons to achieve them. 

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, NaCl). The oxides of group 2 elements have the formula MO, their hydrides are MH2, and their halides are MX2 (for example, CaCb). 

Halogens form a wide variety of oxides and also combine with other halogens. They combine with hydrogen to form HX gases, and these compounds are also commonly used as acids (hydrofluoric, hydrochloric, etc.) in aqueous solution. Halogens form salts with metals by gaining electrons to become X ions. 

Astatine is an exception to many of these properties because it is an artificial metalloid. 

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