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Forming New Substances

Forming New Substances. Chapter 9 - 2 Part 2. Writing Formulas - Ionic Compounds. The formula must have subscripts that cause the charges of the ions to cancel out making the compound neutral. An oxidation number is a positive or negative number. Crisscross Method.

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Forming New Substances

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  1. Forming New Substances Chapter 9 - 2 Part 2

  2. Writing Formulas -Ionic Compounds • The formula must have subscripts that cause the charges of the ions to cancel out making the compound neutral. • An oxidation number is a positive or negative number.

  3. Crisscross Method 1.Write the chemical symbols for each element in the compound (positive 1st) Ex: compound of calcium & chlorine Ca Cl 2. Write the oxidation numbers above the symbols. Ca Cl 3. Crisscross the oxidation numbers making them subscripts.Ca2+ Cl1- 4. Fill in the formula. CaCl2

  4. Continued If they have the same charges or can be reduced, then they cancel each other out. For example: Li 1+ F1- = LiF Al 3+ P 3- = Al3P3 or AlP Ca2+ C4+ = Ca4C2 or Ca2C Pb4+ S2- = Pb2S4 or PbS2

  5. Let’s Practice • 1. Be N • 2. Ca F • 3. Sr P • 4. Ba Pb • 5. Al I • 6. K O • 7. Mg Br • 8. Na Cl

  6. NAMING THE FORMULAS • Ionic compounds do not use prefixes like covalent compounds do. • The second name ends in “ide” just like covalent do. • Examples: Be3N2 Beryllium Nitride or CaF2 is Calcium Fluoride

  7. LET’S TRY IT!

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