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Covalent Compounds. 4.2 Compound Names & Formulas. Covalent molecules share electrons . Covalent bonds occur between two or more non-metals. These molecules exist as solids, liquids or gases. Covalent molecules are like a play-pit full of plastic balls.
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4.2 Compound Names & Formulas • Covalent moleculesshare electrons. • Covalent bonds occur between two or more non-metals. • These molecules exist as solids, liquids or gases. • Covalent molecules are like a play-pit full of plastic balls. • Each plastic ball = 1 covalent molecule of H2O Water, H2O See pages 184 - 185 (c) McGraw Hill Ryerson 2007
4.2 Compound Names & Formulas • The chemical formula of a covalent compound tells us the number of each element in the compound. • Sometimes the names don’t tell us what elements make up the compounds. • Subscripts mean something different in covalent compounds • Ionic compounds subscripts show the smallest whole-number ratio between the ions in the compound. • Covalent molecules have subscripts that show the actual number of atoms in the molecule. Water: H2O Hydrogen Peroxide: H2O2 See page 193 (c) McGraw Hill Ryerson 2007 Methane: CH4
4.2 Compound Names & Formulas • What is the chemical formula for the molecule ethanol? • C2H6O, a name that must be memorized or looked up when needed. • What is the chemical formula for candle wax? • C25H52 • What is the name of the molecule C12O22H11? • Sucrose, also called table sugar. See page 193 (c) McGraw Hill Ryerson 2007
4.2 Compound Names & Formulas • Covalent compounds with 2 non-metal atoms use a system of prefixes. • Prefixes are often used before the atom name to indicate the number of atoms in the molecule. • Example: • CO = carbon monoxide • CO2 = carbon dioxide • CCl4 = carbon tetrachloride See pages 194 - 195 (c) McGraw Hill Ryerson 2007
4.2 Compound Names & Formulas • STEP 1: Write the most metallic atom (farthest left) first • STEP 2: Use prefixes to symbolize the # of each atom. • STEP 3: Add -ide to the end of the second atom’s name See pages 194 - 195 (c) McGraw Hill Ryerson 2007
4.2 Compound Names & Formulas • What is the chemical formula for the molecule trinitrogen tetrachloride? • N3Cl4 • What is the name of the molecule Si3P6? • Trisilicon hexaphosphide See pages 194 - 195 (c) McGraw Hill Ryerson 2007
Covalent Compounds Write the names for the following covalent compounds: 1) P4S5 __________________________________ 2) SeF6 __________________________________ 3) Si2Br6 __________________________________ 4) SCl4 __________________________________ 5) B2Si __________________________________ 6) NF3 __________________________________
Covalent Compounds Write the formulas for the following covalent compounds: 1) antimony tribromide __________________________________ 2) hexaboronsilicide __________________________________ 3) chlorine dioxide __________________________________ 4) iodine pentafluoride __________________________________ 5) dinitrogen trioxide __________________________________ 6) phosphorus triiodide __________________________________