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Writing Names & Formulas for Ionic & molecular compounds - PowerPoint PPT Presentation

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Writing Names & Formulas for Ionic & molecular compounds

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  1. Writing Names & Formulas for Ionic & molecular compounds Textbook Pages: 64 - 68

  2. Valence • Definition: the charge assigned to an ion or atom. • ***Overall, when added the charges must equal ZERO!!! • For Example: • NaCl Na is 1+ Cl is 1− • HCl • N2

  3. Valence • Some elements have more than one valence. • For Example: • PbO O is 2− Therefore, Pb must be 2+ • PbO2 O is 2− Therefore, Pb must be • These elements that have more than one valence are called multivalent elements. • (***See back of Periodic Table)

  4. Naming for Simple Binary Ionic Compounds • Binary means two (2). Therefore, simple binary compounds is the naming of compounds with 2 elements. • The first element only has one valence. • Steps for naming simple binary ionic compounds: • 1. Name the first element regularly from the Periodic Table • 2. Change the ending of the second element to “ide” • For Example: • NaCl Sodium Chloride • Na2O • CaH2

  5. Writing Formulas for Simple Binary Ionic Compounds • Steps for writing simple binary ionic compounds: • 1. Determine the valence for each element in the compound • 2. Criss-cross the valence numbers (ignore the +/− charges) and write them as subscripts • 3. If possible, reduce to the simplest ratio • For Example: • Magnesium Oxide • 1. Mg2+ O2− • 2. Mg2 O2 forms Mg2O2 • 3. Mg2O2 gets reduced to MgO • Aluminum Chloride

  6. Naming Compounds with Multiple Valences • Some elements can have more than one valence. • For Example: Pb can be Pb2+ or Pb4+ • This means it can form 2 compounds that have different chemical and physical properties. • For Example: • Lead Oxide • If lead is 2+, Pb2+ O2−  PbO • If lead is 4+, Pb4+ O2−  • Both these compounds are different from one another!

  7. Naming Compounds with Multiple Valences • One of two methods can be used to distinguish between the compounds that have more than one valence: • Method 1: IUPAC Method • For multiple valence compounds ONLY, we can indicate which one it is my putting its valence in brackets after its name. • For Example: • PbO Lead (II) Oxide • PbO2 Lead (IV) Oxide • Note: Roman Numbers are used I-1, II-2, III-3, IV-4, V-5, VI-6, VII-7 • Method 2: Ous – Ic Method (Classical System) • For multiple valence compounds ONLY, we can indicate the higher valence with an “ic” ending and the lower valence with an “ous” ending. • For Example: • PbO Plumbous Oxide • PbO2 Plumbic Oxide • Note: Often the historical name is used. (***See back of Periodic Table)

  8. Naming and Writing Molecular (Covalent) Compounds • ***Do NOT worry about valences • Steps for naming molecular (covalent) compounds: • 1. Name the first element regularly from the Periodic Table • 2. Change the ending of the second element to “ide” • 3. Use prefixes (below) to say how many atoms of each element are in the compound. • Prefixes: • Mono – 1 Hexa – 6 • Di – 2 Hepta – 7 • Tri – 3 Octa – 8 • Tetra – 4 Nona – 9 • Penta – 5 Deca – 10 • For Example: • Carbon Tetrachloride CF4 • H2O Dihydrogen Monoxide • Note: “Mono” is never used on the first element.

  9. Naming and Writing Molecular (Covalent) Compounds • More Examples: • NO • Nitrogen Trihydride • Diphosphorus Pentoxide • PCl3

  10. Quiz #1 Review • ON BOARD!!!