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Chemistry: Ionic Compounds and Naming

Learn about cations, anions, and polyatomic ions in chemistry, as well as the formation and naming of binary ionic compounds. Includes examples and practice exercises.

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Chemistry: Ionic Compounds and Naming

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  1. Vocabulary - Review Q: What is a cation? A: A positive ion formed by a metal Examples: Na+ Ca 2+ Al 3+ Q: What is an anion? A: A negative ion formed by a nonmetal. Examples: H- F- O 2- P 3- Q: What is a polyatomic ion? A: A group of charged atoms NH4+ SO42- • 1 Chemistry 1/2/2020

  2. Ionic Compounds • Attraction between + ions and - ions • Electrons go from metals to nonmetals electron transfer metal nonmetal ion+ ion– Electrons lost = Electrons gain NOTE: the net charge on the compound is zero

  3. Formation of Ionic Compounds

  4. Ionic Bonding What happens when an atom of sodium reacts with an atom of chlorine? Na Na+ + 1e- Cl + 1e- Cl- Na + Cl + 1e- Na+Cl- + 1e-

  5. Ionic Bonding We write Na+Cl- as simply NaCl • The ionic compound is neutral – this means the net (overall) charge is = 0. • Now let’s try for cesium reacting with sulfur.

  6. Ionic Bonding Cs Cs+ + 1e- S + 2e- S2- Cs + S + 2e- Cs+S2- + 1e- This equation is not balanced. What must be done to correct this? Solution: 1. Write the symbol for each ion present 2.Make sure you include the charge of each ion

  7. Writing a Formula Write the formula for the ionic compound that will form between Ba2+ and Cl. Solution: 1. Balance charge with + and – ions 2. Write the positive ion of metal first, and the negative ion Ba2+ Cl 3. Write the number of ions needed as subscriptsBaCl2 (NOTE WE CRISSCROSSED THE CHARGES)

  8. Ionic Compounds--Example: Sodium and oxygen react • You have to balance the charges. • You do this by criss-crossing the value of the charge (not the + or -) Sodium oxide Na+ O2- Na2O we do not write the 1 as a subscript

  9. Ionic Compounds Lithium iodide Li+ I – LiI

  10. Ionic Compounds Magnesium oxide Mg2+ O2- Mg2O2 MUST be reduced to MgO

  11. Ionic Compounds Let’s try a few: Barium nitride Ba3N2 Aluminum oxide Al2O3 Cesium iodide CsI Sodium fluoride NaF Strontium bromide SrBr2

  12. Learning Check Write the correct formula for the compounds containing the following ions: A. Na+, S2- B. Al3+, Cl- C. Mg2+, N3-

  13. Solution A. Na+, S2- Na2S B. Al3+, Cl- AlCl3 C. Mg2+, N3- Mg3N2

  14. Naming Compounds • Binary Compounds • Composed of two elements • Ionic and covalent compounds included • Binary Ionic Compounds • Metal—nonmetal • Binary Covalent Compounds • Nonmetal—nonmetal

  15. Binary Compounds • Composed of two elements • Binary Ionic Compounds • Metal—nonmetal • Binary Covalent Compounds • Nonmetal—nonmetal

  16. Binary ionic compounds contain positive cations and negative anions. Type I compounds Metal present forms only one cation. Type II compounds Metal present can form 2 or more cations with different charges.

  17. Binary Ionic Compounds (Type I monatomic cations & anions) • Contain 2 different elements • The cation is always named first and the anion second. • A cation has same name as element. Examples: Ca2+ calcium Al3+ aluminum Na + sodium • A anion has the same name as the element name with adding –ideto the end. Examples: Cl- chloride S2- sulfide P3- phosphide

  18. Common Simple Cations and Anions

  19. Rules for Naming Type I Ionic Compounds 1. The cation is always named first and the anion second. 2. A simple cation takes its name from the name of the element. • A simple anion is named by taking the first part of the element name (the root) and adding –ide.

  20. Binary Ionic Compounds (Type I) • Examples: KCl Potassium chloride MgBr2 Magnesium bromide CaO Calcium oxide

  21. Ionic Compounds Now let us put it all together: Na3N Cation: sodium Anion: nitride Compound: Sodium nitride

  22. Ionic Compounds BaO Cation: barium Anion: oxide Compound: barium oxide

  23. Naming Binary Ionic Compounds (Type I) SUMMARY - Name the metal first, then the nonmetal with ending changed to -ide. Examples: NaCl sodium chloride ZnI2 zinc iodide Al2O3 aluminum oxide KCl Potassium chloride MgBr2 Magnesium bromide CaO Calcium oxide

  24. Exercise What is the name of the compound SrBr2? a) strontium bromine b) sulfur bromide c) strontium dibromide d) strontium bromide

  25. Learning Check Complete the names of the following type I binary compounds: Na3N sodium ________________ KBr potassium ________________ Al2O3 aluminum ________________ MgS _________________________

  26. Solution Complete the names of the following binary compounds: Na3N sodium nitride KBr potassiumbromide Al2O3 aluminum oxide MgS magnesium sulfide

  27. Metals in these compounds can form more than one type of positive charge. Charge on the metal ion must be specified. Roman numeral indicates the charge of the metal cation. Transition metal cations usually require a Roman numeral. Binary Ionic Compounds (Type II)

  28. Binary Ionic Compounds (Type II) • Metals in these compounds form more than one type of positive charge. • Charge on the metal ion must be specified. • Roman numeral indicates the charge of the metal cation. • Transition metal cations that form 2 or more positive ions require a Roman numeral. 1+ or 2+ ____________________ 2+ or 3+ • Cu+, Cu2+ Fe2+, Fe3+ • copper(I) ion iron(II) ion • copper (II) ion iron(III) ion

  29. Common Type II Cations

  30. Rules for Naming Type II Ionic Compounds 1. The cation is always named first and the anion second. 2. Because the cation can assume more than one charge, the charge is specified by a Roman numeral in parentheses.

  31. Binary Ionic Compounds (Type II) • Examples: CuBr Copper(I) bromide FeS Iron(II) sulfide PbO2 Lead(IV) oxide

  32. Binary Ionic Compounds (Type II) Use a roman number after the name of a metal that forms two or more ions (note compound is neutral) Example: FeCl3(Fe3+) iron (III) chloride CuCl (Cu+ ) copper (I) chloride SnF4 (Sn4+) tin (IV) fluoride PbCl2 (Pb2+) lead (II) chloride Fe2S3 (Fe3+) iron (III) sulfide

  33. Exercise What is the name of the compound CrO2? a) chromium oxide b) chromium(II) oxide c) chromium(IV) oxide d) chromium dioxide

  34. Exercise What is the correct name of the compound that results from the most stable ion for sulfur and the metal ion that contains 24 electrons? a) iron(III) sulfide b) chromium(II) sulfide c) nickel(III) sulfate d) iron(II) sulfide

  35. Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr2 iron (_____) bromide Cu2O copper (_____) oxide SnCl4 ___(_____ ) ______________ Fe2O3 ________________________ CuS ________________________

  36. Solution Complete the names of the following binary compounds with variable metal ions: FeBr2 iron ( II ) bromide Cu2O copper ( I ) oxide SnCl4tin (IV) chloride Fe2O3iron (III) oxide CuS copper (II) sulfide

  37. Learning Check Name the following compounds: A. CaO B. SnCl4 C. Co2O3

  38. Solution Name the following compounds: A. CaO calcium oxide B. SnCl4tin(IV) chloride C. Co2O3cobalt (III) oxide

  39. Polyatomic ions are charged entities composed of several atoms bound together. • They have special names and must be memorized. (see Table 2.5 on pg. 62 in text). • Examples of compounds containing polyatomic ions: • NaOH Sodium hydroxide • Mg(NO3)2 Magnesium nitrate • (NH4)2SO4 Ammonium sulfate

  40. Names of Common Polyatomic Ions

  41. Naming ionic compounds containing polyatomic ions follows rules similar to those for binary compounds. • Ammonium acetate

  42. Examples NaOH Sodium hydroxide Mg(NO3)2 Magnesium nitrate (NH4)2SO4 Ammonium sulfate FePO4 Iron(III) phosphate

  43. Exercise What is the name of the compound KClO3? a) potassium chlorite b) potassium chlorate c) potassium perchlorate d) potassium carbonate

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