Chapter 7.1 : Chemical Names and Formulas


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Chapter 7.1 : Chemical Names and Formulas

  1. 1. Chemical Formulas and chemical compounds<br />Chapter 7.1<br />
  2. 2. Objectives:<br />Explain the significance of a chemical formula.<br />Determine the formula of an ionic compound formed between two given ions.<br />Name an ionic compound given its formula.<br />Using prefixes, name a binary molecular compound from its formula.<br />Write the formula of a binary molecular compound given its name.<br />
  3. 3. Chemical names and Formulas<br />There are millions of natural and synthetic chemical compounds<br />Calcium carbonate – limestone<br />Sodium chloride – table salt<br />Dihydrogen monoxide – water<br />These are their chemical and common names<br />Chemical names help to describe the atomic makeup of the compounds<br />
  4. 4. Significance of a Chemical Formula<br />Chemical formula<br />Indicates the relative number of atoms of each kind in a chemical compound.<br /><ul><li>Molecularformula
  5. 5. Indicates the relative number of atoms of each kind in a molecule. (Covalently bonded)</li></ul>C8H18<br />Subscript indicates there are 8 atoms of carbon in a molecule of octane<br />Subscript indicates there are 18 atoms of hydrogen in a molecule of octane<br />
  6. 6. Chemical formula for ionic compound<br />Ionic compound consists of lattice of positive and negative ions held together by mutual attraction.<br />Chemical formula represented by one formula unit<br />Simplest ratio of the compounds positive and negative ions<br />Aluminum sulfate below consists of aluminum cations and sulfate ions<br />Al2(SO4)3<br />Subscript 3 refers to everything inside the parentheses giving 3 sulfate ions, with a total of 3 sulfur atoms and 12 oxygen atoms<br />Subscript 2 refers to 2 Aluminum atoms<br />Subscript 4 refers to 4 oxygen atoms in the sulfate ion<br />Note: when you only have one of an atom, no subscript is used<br />Note: parentheses are used to identify polyatomic ion as one unit<br />
  7. 7. Monatomic ions<br />Ions formed from a single atom<br />Examples<br />Na+1 lose one electron<br />Mg2+ <br />S2- gain two electrons<br />N-3<br />Cl1-<br /><ul><li>Not all main-group elements readily form ions
  8. 8. Examples
  9. 9. Carbon & Silicon form covalent bonds
  10. 10. d-block elements form variable charges
  11. 11. examples
  12. 12. Copper, can be Cu+1 or Cu+2
  13. 13. Iron, can be Fe+2 or Fe+3
  14. 14. Lead, can bePb+2, Pb+3, or Pb+4</li></li></ul><li>Naming Monatomic ions<br />Positive ions<br />Name of element<br />Ex: K+ Potassium<br /> Mg+2 Magnesium<br /> Al+3 __________<br /> Sr+2 __________<br /><ul><li>Negative ions
  15. 15. Base of element + -ide ending
  16. 16. Ex: F-1 Fluoride</li></ul> N-3 Nitride<br /> O-2 _______<br /> Br-1 _______<br />
  17. 17. Binary Ionic Compounds<br />Compounds composed of two different elements<br />Total # of positive charges must be equal to total # of negative charges<br /><ul><li>Writing formulas, Ex: Aluminum oxide</li></ul>Write the symbols for ions (Cation first)<br /> Al+3 O-2<br />Cross over the charges as subscripts<br /> Al2O3<br />Check to make sure total charges are equal, divide by largest number, to give smallest whole-number ratio<br /> Al2O3<br />+3<br />-2<br />2 x (+3) = +6<br />3 x (-2) = -6<br />
  18. 18. Naming binary ionic compounds<br />Nomenclature<br />Naming system<br /><ul><li>Name Al2O3
  19. 19. Name cation first : full name of cation
  20. 20. Aluminum
  21. 21. Name Anion last : base of anion + -ide
  22. 22. oxide</li></ul>Al2O3<br />aluminum oxide<br />
  23. 23. Practice Naming and Writing Formulas<br />Name<br />AgCl<br />ZnO<br />SrF2<br />silver chloride<br />zinc oxide<br />strontium fluoride<br /><ul><li>Write the formulas for</li></ul>Zinc iodide<br />Zinc sulfide<br />Aluminum sulfide<br />ZnI2<br />ZnS<br />Al2S3<br />
  24. 24. Stock System of Nomenclature<br />Some cations may have two or more different charges<br />Use stock system of naming (usually with d-block elements)<br /><ul><li>Roman numeral represents charge in parentheses
  25. 25. Fe+2 Fe+3</li></ul> Iron(II) Iron(III)<br /><ul><li>Some cations that commonly form only one cation
  26. 26. Do not use roman numerals ( main group elements)
  27. 27. No Anions form more than one charge</li></ul>+2<br />-1<br />CuCl2<br />copper(II)<br />chloride<br />
  28. 28. Practice stock system<br />Write formula and give name for compound formed by ions Cr+3 and F-1<br />CrF3<br />chromium(III) fluoride<br /><ul><li>Write formulas and give name for the following ionic compounds:</li></ul>CuBr2<br /> copper(II) bromide<br />Cu+2 and Br-1<br />Fe+2 and O-2<br />FeO<br /> iron(II) oxide<br />Fe+3 and O-2<br />Fe2O3<br /> iron(III) oxide<br />
  29. 29. Compounds containing Polyatomic Ions<br />All but NH4+, ammonium ion, are negatively charged<br />Most are oxyanions<br />Examples<br />NO3-1 NO2-1<br />nitrate<br />nitrite<br /><ul><li>Most common anion has –ate ending
  30. 30. Anion with one less oxygen has –ite ending
  31. 31. Anion with two less oxygen has hypo prefix and –ite ending
  32. 32. Anion with one extra oxygen has per prefix and –ate ending</li></ul>ClO3-1<br />ClO2-1<br />ClO-1<br />ClO4-1<br />hypochlorite<br />perchlorate<br />chlorate<br />chlorite<br />
  33. 33. Naming Compounds with Polyatomic Ions<br />Same as naming for ionic compounds except<br />Name polyatomic ion as one unit<br />Example:<br />AgNO3<br />Use parentheses if more than one polyatomic ion<br />Example<br />Al2(SO4)3<br />silver nitrate<br />Show 2 Al+3 ions and 3 SO4-2 ions<br />aluminum sulfate<br />
  34. 34. Writing Formulas and Naming Compounds with Polyatomic Ions<br />Write the formula for these:<br />tin(IV) sulfate<br />calcium chloride<br />lithium nitrate<br />calcium nitrite<br />potassium perchlorate<br />Sn(SO4)2<br />CaCl2<br />LiNO3<br />Ca(NO2)2<br />KClO4<br /><ul><li>Write the names for these:</li></ul>Ag2O<br />Ca(OH)2<br />NH4OH<br />FeCrO4<br />KClO<br />silver oxide<br />calcium hydroxide<br />ammonium hydroxide<br />iron(II) chromate<br />potassium hypochlorite<br />
  35. 35. Naming Binary Molecular Compounds<br />May use stock system to name these<br />New system – must understand oxidation numbers<br /><ul><li>Prefix system
  36. 36. Old system – must know numerical prefixes</li></ul>mono-<br />di-<br />tri-<br />tetra-<br />penta-<br />hexa-<br />hepta-<br />octa-<br />nona-<br />deca-<br />
  37. 37. Rules for prefix system of Nomenclature<br />less-electronegative element is given first<br />Second element is named by combining<br />Prefix indicating number of atoms<br />Root of name of second element<br />-ide ending<br /><ul><li> First element only gets a prefix if it has more than one</li></ul>Ex: P4O10<br />Ex:<br />tetra<br />phosphorus<br />dec<br />ox<br />ide<br />The o or a at the end of a prefix is usually dropped when the word following the prefix begins with another vowel<br />
  38. 38. The 6 binary compounds of Nitrogen and Oxygen<br />N2O<br />NO<br />NO2<br />N2O3<br />N2O4<br />N2O5<br />dinitrogen<br />monoxide<br />nitrogen<br />monoxide<br />dioxide<br />nitrogen<br />dinitrogen<br />trioxide<br />dinitrogen<br />tetroxide<br />pentoxide<br />dinitrogen<br /><ul><li>Name the following molecular compounds
  39. 39. Write formulas for the following molecular compounds</li></ul>SO3<br />ICl3<br />PBr5<br />sulfur trioxide<br />carbon tetraiodide<br />phosphorus trichloride<br />oxygen difluoride<br />CI4<br />iodine trichloride<br />PCl3<br />Phosphorus pentabromide<br />OF2<br />