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Section 2.3—Chemical Formulas

Section 2.3—Chemical Formulas. We need to be able to read the formulas for chemicals in the antacids!. Reminders from Section 2.2. Your Appendix (Page A-2) has lists of: Common polyatomic ions Multivalent metals Covalent prefixes

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Section 2.3—Chemical Formulas

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  1. Section 2.3—Chemical Formulas We need to be able to read the formulas for chemicals in the antacids!

  2. Reminders from Section 2.2 • Your Appendix (Page A-2) has lists of: • Common polyatomic ions • Multivalent metals • Covalent prefixes • Use your periodic table to determine the charges of common elements when they form ions

  3. Binary Ionic compounds

  4. Ionic Compound Definitions Ionic bond- bond formed by attraction between + and - ions Binary Ionic Compound- compound containing two elements—one metal and one non-metal + Cation - Anion

  5. Metals & Non-Metals Ionic Bonds are between metals & non-metals

  6. Identifying & Naming Binary Ionic • These compounds: • End in “-ide” (except “hydroxide and cyanide”) • Do NOT contain covalent prefixes • To write these formulas: • Write the symbol & charge of the first element (the metal, cation) • Write the symbol & charge of the second element (the non-metal, anion) • Add more of the cations and/or anions to have a neutral compound • Use subscripts to show how many of each type of ion is there.

  7. Example #1 Sodium chloride

  8. Example #1 Na+1 Cation Sodium chloride Anion Cl-1 NaCl

  9. Example #1 Na+1 Cation Na+1Cl-1 Sodium chloride +1 + -1 = 0 Anion The compound is neutral…no subscripts are needed. Cl-1 NaCl

  10. Example #2 Calcium bromide

  11. Example #2 Ca+2 Cation Calcium bromide Anion Br-1

  12. Example #2 Ca+2 Cation Ca+2Br-1 Calcium bromide +2 + -1 = +1 Anion Ca+2Br-1Br-1 Br-1 +2 + -1 + -1 = 0 CaBr2 The subscript “2” is used to show that 2 anions are needed.

  13. Let’s Practice Cesium chloride Potassium oxide Calcium sulfide Lithium nitride Example: Write the following chemical formulas

  14. Let’s Practice Cesium chloride Potassium oxide Calcium sulfide Lithium nitride CsCl K2O CaS Li3N Example: Write the following chemical formulas

  15. Polyatomic Ionic Compounds

  16. Polyatomic Ionic Compound - Polyatomic Anion Definition Polyatomic Ion- more than one atom that together have a charge Polyatomic Ionic Compound- compound containing at least one polyatomic ion + Cation

  17. Identifying & Naming Polyatomic Ionic • These compounds: • Do not end with “-ide” (except hydroxide & cyanide) • Do not use covalent prefixes • To write these formulas: • Write the symbol & charge of the cation & anion • Add additional cations or anions to have a neutral compound • Use subscripts to show the number of ions • When using subscripts with a polyatomic ion, you must put the polyatomic ion in parenthesis.

  18. Example #3 Sodium carbonate

  19. Example #3 Na+1 Cation Sodium carbonate Polyatomic Anion CO3-2

  20. Example #3 Na+1 Cation Na+CO32- Sodium carbonate +1 + -2 = -1 Polyatomic Anion Na+Na+CO32- +1 + 1 + -2 = 0 CO3-2 Na2CO3 The subscript “2” is used to show that 2 cations are needed.

  21. Example #4 Magnesium nitrate

  22. Example #4 Mg+2 Cation Magnesium nitrate Polyatomic Anion NO3-1

  23. Example #4 Mg+2 Mg+2NO3- Cation +2 + -1 = 1 Magnesium nitrate Mg+2NO3- NO3- Polyatomic Anion +2 + -1 + -1 = 0 NO3-1 The subscript “2” is used to show that 2 anions are needed. Mg(NO3)2 Use parenthesis when adding subscripts to polyatomic ions

  24. Let’s Practice Sodium nitrate Calcium chlorate Potassium sulfite Calcium hydroxide Example: Write the following chemical formulas

  25. Let’s Practice Sodium nitrate Calcium chlorate Potassium sulfite Calcium hydroxide NaNO3 Ca(ClO3)2 K2SO3 Ca(OH)2 Example: Write the following chemical formulas

  26. Multivalent Metals

  27. Definition Multivalent Metal- metal that has more than one possibility for cationic charge

  28. Identifying & Naming Multivalent Metals • These compounds: • Will have roman numerals • To write these formulas: • Same as binary ionic or polyatomic ionic. • The roman numerals tell the charge of the metal (cation)

  29. Example #5 Iron (III) oxide

  30. Example #5 Fe+3 Cation Iron (III) oxide Anion O-2

  31. Example #5 Fe+3 Fe+3O2- Cation +3 + -2 = -1 Iron (III) oxide Fe+3Fe+3O2-O2- Anion +3 + 3 + -2 + -2 + -2 = 0 O-2 The subscript “2” and “3” are used to show the numbers of atoms needed. Fe2O3

  32. Example #6 Copper (II) nitrate

  33. Example #6 Cu+2 Cation Copper (II) nitrate Polyatomic Anion NO3-1

  34. Example #6 Cu+2 Cu+2NO3- Cation +2 + -1 = 1 Copper (II) nitrate Cu+2NO3-NO3- Polyatomic Anion +2 + -1 + -1 = 0 NO3-1 Use parenthesis when adding subscripts to a polyatomic ion Cu(NO3)2

  35. Let’s Practice Iron (II) nitrate Copper (I) chloride Lead (IV) hydroxide Tin (II) oxide Example: Write the following chemical formulas

  36. Let’s Practice Iron (II) nitrate Copper (I) chloride Lead (IV) hydroxide Tin (II) oxide Fe(NO3)2 CuCl Pb(OH)4 SnO Example: Write the following chemical formulas

  37. Binary Covalent Compounds

  38. Covalent compound Definition Covalent bond atoms share electrons Binary Covalent Compound compound made from two non-metals that share electrons Non metal Non metal

  39. Identifying & Naming Binary Covalent • These compounds: • Use covalent prefixes • To write these formulas: • Write the symbols of the first and second element • Use the covalent prefixes (assume the first element is “1” if there’s no prefix) as the subscripts to show number of atoms. Atoms do not form charges when bonding covalently…you DO NOT need to worry about charges with this type!

  40. Example #7 Dinitrogen Tetraoxide

  41. Example #7 “Di-” = 2 N Dinitrogen Tetraoxide O “Tetra-” = 4 N2O4

  42. Example #8 Silicon dioxide

  43. Example #8 “Mono-” is not written for the first element Si Silicon dioxide O “Di-” = 2 SiO2

  44. CAUTION!!! “di” and “bi” do not mean the same thing! di- bi- Stands for “2” in covalent compounds Means there’s a hydrogen in the polyatomic anion Carbon dioxide = CO2 Sodium biphosphate = Na2HPO4

  45. Let’s Practice Carbon monoxide Nitrogen dioxide Diphosphorus pentaoxide Example: Write the following chemical formulas

  46. Let’s Practice Carbon monoxide Nitrogen dioxide Diphosphorus pentaoxide CO NO2 P2O5 Example: Write the following chemical formulas

  47. Nomenclature Summary

  48. Mixed Practice Magnesium hydroxide Copper (II) nitrate Iron (III) oxide Nitrogen dioxide Sodium bicarbonate Example: Write the following chemical formulas

  49. Mixed Practice Magnesium hydroxide Copper (II) nitrate Iron (III) oxide Nitrogen dioxide Sodium bicarbonate Mg(OH)2 Cu(NO3)2 Fe2O3 NO2 NaHCO3 Example: Write the following chemical formulas

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