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Names & Formulas

Names & Formulas. Ionic Compounds 8.3. Formulas. Formula unit is the ratio of cations to anions’ Total number of electrons lost by cations must equal total number of electrons gained by anions Binary compounds = simplest compound = 2 atoms One cation, one anion

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Names & Formulas

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  1. Names & Formulas Ionic Compounds 8.3

  2. Formulas • Formula unit is the ratio of cations to anions’ • Total number of electrons lost by cations must equal total number of electrons gained by anions • Binary compounds = simplest compound = 2 atoms • One cation, one anion • Monatomic ion = ion made from one atom

  3. Typical Ions • See Book, page 221 • Oxidation number = oxidation state = number of electrons transferred from an atom to make a compound • Na+ oxidation number = +1 • O2- oxidation number = 2- • Used to determine compound formulas

  4. Formula Names • Remember: total number of electrons lost by cations must equal total number of electrons gained by anions! • Metal name is stated first. • Number of cations in ratio is subcripted • Nonmetal name is stated second • Suffix –ide is used • Number of anions in ration is subscripted

  5. Formula Names • Examples • Sodium (Na+) and Chlorine (Cl-) NaCl = ratio 1:1 Sodium Chloride • Calcium (Ca2+) and Fluorine (Fl-) CaFl2 = ratio 1:2 Calcium Fluoride Aluminum (3+) and Sulfur (2-) Find lowest common dominator (6) 2(Al 3+) + 3 (S 2+) = both transfer 6 electrons Al2S3 Aluminum Sulfide

  6. Formulas with Polyatomic Ions • Poly atomic ions stay together as a single group • Example Calcium and Phosphate • Calcium (2+) • Phosphate PO4 (3-) • 3 (Ca) + 2 ( PO4) • Ca3(PO4)2 • Calcium Phosphate

  7. Naming Polyatomic Compounds • Oxyanions = polyatomic anions with one or more oxygen atom • With 2 anion forms: • Anion with most oxygen atoms is –ate • Anion with fewer oxygen atoms is –ite • With multiple anion forms: • Most oxygen atoms is per- metal -ate • Second most oxygen is –ate • Third most oxygen atoms is –ite • Fourth most oxygen atoms is hypo- metal -ite

  8. Naming Review • Name cation first, anion second • Monatomic ions use atom name • Monatomic anions take root of name and add –ide suffix • Group 1A and 2A metals have only one oxidation state. Transition metals can have more than one. Put oxidation state in as roman numerals • Polyatomic ions – just name the ion

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