Combining Power The number of electrons that an element can lose, gain, or share is called its Oxidation Number. All the positive ions have to equal the negative ions. For example: NaCl or AlCl 3 In a compound, the sum of the oxidation numbers is ZERO. *
·Some elements have more than one oxidation number. For example: Iron = 2+ or 3+. …. Fe(II) or Fe(III). Roman numeral following the symbol tells the oxidation number!
ElementValenceOxida-tion # ElementValenceOxida-tion # Formula AluminumChlorine MagnesiumBromine SodiumOxygen LithiumOxygen CalciumPhosphoro us CarbonChlorine AluminumOxygen BerylliumSulfur SodiumFluorine SiliconNeon
Writing Formulas for Ionic Compounds 1. Write the symbols (write the positive ion first). 2. Write the oxidation number over the top of each symbol.. Reduce if possible. 3. Criss-Cross the oxidation numbers and make them subscripts.
Naming Ionic Compounds (Metal & Nonmetal) *Name the 1st element then Name the 2nd element with "IDE" ending. For example: NaCl = Sodium Chloride BaF 2 = Barium Fluoride Al 2 O 3 = Aluminum Oxide
Electron Sharing: Covalent Bonds ·Electrons are sometimes SHARED between the atoms. The valence levels join together. The bond is called ___________________. ·The smallest unit of a covalently bonded compound is called a ____________. For example: The bond between Hydrogen and Chlorine. (See Page ____________)
Some ELEMENTS exist in nature as covalent bonds. They are called_ D iatomic Molecules T he ‘Heavenly 7’
Naming Covalent Bonds · A prefix is used before the name of an element to indicate the number of atoms in that compound.... CO 2 = Carbon Dioxide CO = Carbon Monoxide
· 'Mono" is only used before the second element in a compound. It is never used for the first. (All other prefixes are used for the first element. For example: CO = Carbon Monoxide C 2 O 2 = Dicarbon Dioxide