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Writing and Naming Binary Compounds & Hydrates

Writing and Naming Binary Compounds & Hydrates. You will need: A periodic table A list of common polyatomic ions Patience and understanding. Generic Chemical Formulas. MgCl 2. Chemical symbols. Subscript. Binary Compounds.

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Writing and Naming Binary Compounds & Hydrates

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  1. Writing and Naming Binary Compounds & Hydrates You will need: A periodic table A list of common polyatomic ions Patience and understanding

  2. Generic Chemical Formulas MgCl2 Chemical symbols Subscript

  3. Binary Compounds A chemical compound consisting of two parts, a CATION (+) and an ANION (-) Examples: • Two elements chemically bonded • 2. An element and a polyatomic ion chemically bonded • 3. Two polyatomic ions chemically bonded

  4. Binary Compounds Have two parts Left side is the cation Positively charged Right side is the anion Negatively charged MgCl2

  5. Hydrates A hydrate is a binary compound that has water attached to its ions and the water is a PART of the chemical formula. Naming hydrates uses terms that indicate the number of water molecules.

  6. Hydrates CaSO4 • 2 H2O Calcium sulfate dihydrate Binary compound AlO3 • 3 H2O Aluminum oxide trihydrate Binary compound CuSO4 • 5 H2O Copper (II) sulfate pentahydrate Binary compound

  7. Writing Binary Formulas 6 Steps 1. Write chemical symbols for cation and anion 2. Add cation and anion oxidation numbers as superscripts 3. Check to see if oxidation numbers add to zero 4. If yes, leave as written 5. If no, make oxidation numbers subscripts 6. Check for lowest whole number ratio

  8. Writing Binary Formulas Write the formula for sodium chloride. + - Na Cl 3 4 1 2 Add cation and anion oxidation numbers as superscripts Check to see if oxidation numbers add to zero If yes, leave as written Write chemical symbols for the cation and anion

  9. Writing Binary Formulas Write the formula for magnesium nitride +2 -3 Mg N 3 2 3 4 5 1 2

  10. Writing Binary Formulas Write the formula for hydrogen carbonate + -2 H CO3 2 3 4 5 1 2

  11. Writing Binary Formulas Write the formula for magnesium phosphate -3 +2 ( ) Mg PO4 2 3 3 4 5 1 2

  12. Writing Binary Formulas For transition metals the oxidation number is given in parentheses, In Roman numerals. Write the formula for iron (III) oxide. Fe +3 O -2 Fe2 O3

  13. Writing Binary Formulas • For hydrates, that is, binary compounds with water (hydrate) attached: • nickel (II) sulfate hexahydrate • Write the formula of the binary compound (first part) using rules 1-4: • NiSO4 • b. Insert a “raised dot” after the binary compound: • NiSO4● • Use name prefix to note the number of water molecules (hydrates): • NiSO4 ●6 H2O

  14. Polyatomic Ions (learn these) Table 4 Page 619

  15. More Polyatomic Ions (learn these, too)

  16. A quick review of hydrates.

  17. Naming Binary Formulas Binary Compound = CATION + ANION First: Get a periodic table and table of common polyatomic ions Next: Determine the cation and anion in the compound Then: Note the cation and apply the 5 naming rules IN ORDER

  18. Naming Binary Formulas 5 Rules that begin with the location or kind of the CATION Rule 1. For elements in the first two columns of the periodic table Rule 2. For elements from group 3 up to the staircase Rule 3. For elements to the right (above) the staircase Rule 4. For CATIONS that are polyatomic ions Rule 5. For hydrates

  19. Naming Binary Formulas – Rule 1 • For cations (elements) in the first two columns of the periodic • table: • MgCl2 LiOH • Cation: Write the name of the element as the first part of the compound: • magnesium lithium • b. Anion: Write the name of the element with an ide ending: • magnesium chloride • Anion: Write the name of the polyatomic ion: • lithium hydroxide or

  20. Naming Binary Formulas – Rule 2 • For cations (elements) from the third group of the periodic table up to the “staircase” • FeCl2 Cu2SO4 • Cation: Name of element with Roman Numeral to show oxidation number: • iron (II) copper (I) • b. Anion: Name the element with an ide ending: • iron (II) chloride • Anion: Name the polyatomic ion: • copper (I) sulfate Exceptions to rule: Ag+1 Zn+2 Cd+2 Al+3 (Use Rule 1) or

  21. Naming Binary Formulas – Rule 3 • For cations (elements) to the right (above) the “staircase” • CO2 CO N4S3 • Count the “number” of each element. (C-1, O-2 C-1, O-1N-4, S-3) • b. Use prefixes (mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca) to indicate the number of each atom present. • Do not use “mono” if there is only one of the first element in the compound. • CO2 N4S3 • CARBON DIOXIDE CO TETRANITROGEN TRISULFIDE CARBON MONOXIDE

  22. Naming Binary Formulas – Rule 4 • For cations that are polyatomic ions: • NH4Cl NH4OH • Cation: Name the polyatomic ion: • ammonium ammonium • b. Anion: Name the element with an ide ending: • ammonium chloride • Anion: Name the polyatomic ion: • ammonium hydroxide or

  23. Naming Binary Formulas – Rule 5 • For hydrates, that is, binary compounds with water (hydrate) attached: • NiSO4● 6 H2O • Name of the binary compound (first part) using rules 1-4: • nickel (II) sulfate • b. Note the number of water molecules (hydrates) by using prefixes: • nickel (II) sulfatehexahydrate

  24. Rest stop! Inhale and breathe easy! The next group of slides goes into some detail about oxidation numbers in covalent compounds and in polyatomic ions. For this presentation, a periodic table that shows electronegativities is most helpful.

  25. Covalent Compounds Example: phosphate ion Electronegativity: 2.1 3.5 -2 P O43- Polyatomic ion with a charge = -3 Since oxygen is the more electronegative element, it will have its normal oxidation number.

  26. Covalent Compounds Example: • + 5 • 8 • - 3 +5 -2 P O43- The phosphate ion has a charge of negative three, so the oxidation numbers must add up to the total charge of the ion.

  27. Ionic Compounds with Polyatomics Example: +2 Ca SO4 This is an ionic compound, so the charge of the metal cation is its oxidation number

  28. Ionic Compounds with Polyatomics Example: +2 Ca SO4 The anion is a polyatomic ion, sulfate, and the charge of sulfate is negative two. So the oxidation numbers of sulfur and oxygen must add to -2

  29. Ionic Compounds with Polyatomics Example: 2.5 3.5 +2 -2 Ca SO4 Oxygen is the more electronegative of the two, so it keeps its normal oxidation number.

  30. Ionic Compounds with Polyatomics Example: +6 -2 Ca SO4 +2 Sulfur and the four oxygen atoms must add to negative two (the charge of the sulfate anion).

  31. Ionic Compounds with Polyatomics Example: Pb(OH)4 This is an ionic compound, so the charge of the metal cation is its oxidation number. But this is a transition metal, so we cannot know it from its position on the periodic table.

  32. Ionic Compounds with Polyatomics Example: +4 -1 Pb(OH)4 But the anion, the hydroxide ion, carries a charge of negative one. All four hydroxides are negative one, but since the compound is neutral, the oxidation number of lead must balance it out.

  33. Ionic Compounds with Polyatomics Example: 3.5 2.1 +4 -2 Pb(OH)4 Within the anion, oxygen is the more electronegative of the two elements, and keeps its normal oxidation number.

  34. Ionic Compounds with Polyatomics Example: +4 -2 +1 Pb(OH)4 Within the hydroxide ion, the oxygen and hydrogen must add to the charge of the ion, -1

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