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Chemical Formulas Review

Chemical Formulas Review. Transition Metals and Polyatomic Ions. Transition Metals. Recall: Transition metals (with few exceptions) form cation with more than one possible charge Ex: Fe  Fe 2+ , Fe 3+ ; Pb  Pb 2+ , Pb 4+ In ionic compounds, these charge are also their oxidation numbers

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Chemical Formulas Review

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  1. Chemical Formulas Review Transition Metals and Polyatomic Ions

  2. Transition Metals • Recall: • Transition metals (with few exceptions) form cation with more than one possible charge • Ex: Fe Fe2+, Fe3+; Pb Pb2+, Pb4+ • In ionic compounds, these charge are also their oxidation numbers • We can write balanced chemical formulas by using the cross-over method

  3. Example • A compound containing an Sn2+ ion and a Cl- ion: 1. Sn2+ Cl- 2.Sn2+1Cl-2 3. SnCl2 • Practice! Write formulas that contain the following: Pb4+ ion and O2- ion Cr3+ ion and I- ion

  4. Transition Metals, cont. • Sometimes you will see a Roman numeral in parenthesis written after the name of the metal • This represents the charge/ oxidation number of the ion • Ex: Copper(II) ion  Cu2+ ion

  5. Naming Compounds with Transition Metals • Stock System • Name the metal first • Include the charge of the ion as a Roman numeral in parenthesis immediately after • Name the nonmetal second Ex: CuCl2 copper(II) chloride PbBr4 lead(IV) bromide Practice: HgS Fe2O3 CoF3

  6. Polyatomic ions • Ions that contain more than one atom • Oxyanions- contain oxygen + another nonmetal • Negatively charged/ negative oxidation numbers • Only exception is ammonium (NH4+)

  7. Know These Polyatomic Ions!

  8. Writing Chemical Formulas with Polyatomic Ions • Use the crossover technique • Do NOT change the subscripts of the ions!!! • If the compound contains more than one of that ion, put the ion in parenthesis, and place the subscript outside the parenthesis

  9. Example A compound containing Ca2+ ion and NO3- polyatomic ion • Ca2+NO3- • Ca2+ 1(NO3) -2 • Ca(NO3)2 Practice! Write formulas containing the following: Na+ ion and CO32- ion Mg2+ ion and OH- ion

  10. Naming Compounds Containing Polyatomic Ions • Name metal first (watch out for transition metals!) • Name polyatomic ion second • Only exception is with ammonium- it is always named first

  11. Homework: Due 11-6-2012 Write balanced chemical formulas that contain the following: 1. Cr3+ ion and NO3- ion 2. Li+ and CrO42- ion 3. Sn4+ ion and N3- ion 4. NH4+ ion and PO43- ion 5. Al3+ and CO32- ion • Name the following compounds: • PbMnO4 • NaNO2 • (NH4)3PO4 • MgSO4 • Na2O2

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