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Naming Compounds and Writing Formulas

Naming Compounds and Writing Formulas. Chapter 2 (2.6 and 2.7). Writing Names for Ionic Compounds. Write the name of the cation followed by the name of the anion Ending of monatomic anions must be changed to –ide Include Roman numerals for metals that have variable charges

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Naming Compounds and Writing Formulas

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  1. Naming Compoundsand Writing Formulas Chapter 2 (2.6 and 2.7)

  2. Writing Names for Ionic Compounds • Write the name of the cation followed by the name of the anion • Ending of monatomic anions must be changed to –ide • Include Roman numerals for metals that have variable charges • Groups 1 & 2, Al, Zn, Ag, Cd do not need Roman Numerals

  3. Naming Hydrates • The ONLY time that you use the numerical prefixes with ionic compounds is to indicate the number of water molecules attached to a hydrated ionic compound CuSO4. 5H2O copper (II) sulfate pentahydrate

  4. Oxides (O2-) • Metals and nonmetal combine with oxygen to form oxides • Examples: CaO is calcium oxide PtO2 is platinum (IV) oxide

  5. Peroxides (O22-) • Active metals (group 1 except Li, group 2 except Be & Mg) may combine with oxygen to form peroxides • Each oxygen is 1- • Example: CaO2 is calcium peroxide • H2O2 is hydrogen peroxide; H can act as an active metal

  6. Superoxides (O2-) • Very active metals (K, Rb, Cs) may combine with oxygen to form superoxides • Each oxygen is -1/2 • Example: RbO2 is rubidium superoxide

  7. KO2 K2O2 K2O potassium superoxide potassium peroxide potassium oxide Name these Oxides

  8. Names and Formulas for Binary Molecular Compounds • Binary molecular compounds contain two elements. • The most metallic element (i.e., the one farthest to the left on the periodic table) is usually written first. Exception: NH3 (ammonia) • If both elements are in the same group, the lower one is written first. Example: SO2

  9. Greek prefixes (page 63) are used to indicate the number of atoms (mono, di, tri). • The first letter is omitted when o-o or a-o combinations occur. • The prefix mono is never used with the first element (Example: carbon monoxide, CO). Examples: Cl2O dichlorine monoxide N2O4 dinitrogen tetroxide NF3 nitrogen trifluoride P4S10 tetraphosphorus decasulfide

  10. Writing empirical formulas for ionic compounds • You must combine cations and anions in a ratio so that the total positive charge is equal to the total negative charge • Use the criss cross method

  11. Binary Ionic Compounds • Contain atoms of two elements • Write the chemical formula by using the criss cross method CaI2

  12. Subscripts must be reduced since an empirical formula shows the lowest whole number ratio of ions or atoms Ca2O2 must be reduced to CaO

  13. Ternary Ionic Compounds • Contain atoms of three elements • Parentheses must be placed around polyatomic ions to separate the ion from the subscript when more than one ion is needed Ca(OH)2

  14. Charges of Ions Group Charge 1 1+ 2 2+ 3 3+ 15 3- 16 2- 17 1-

  15. Names and Formulas of Acids • The names of acids are related to the names of anions: • -ide becomes hydro- ...-ic acid; HCl hydrochloric acid •  -ate becomes –ic acid; HClO4 perchloric acid •  -ite becomes –ous acid. HClO hypochlorous acid

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