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Naming Chemical Compounds

Naming Chemical Compounds. 3221.3.1, 3221.3.2. Objectives. TLW write chemical formulas of ionic and molecular compounds. TLW name chemical compounds using the correct system. TLW use polyatomic ions. Significance of a chemical formula.

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Naming Chemical Compounds

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  1. Naming Chemical Compounds 3221.3.1, 3221.3.2

  2. Objectives TLW write chemical formulas of ionic and molecular compounds. TLW name chemical compounds using the correct system. TLW use polyatomic ions.

  3. Significance of a chemical formula • Recall that a chemical formula indicates the relative number of atoms of each kind in a chemical formula C8H18 • Hydrocarbon: molecular compounds composed only of hydrogen and carbon

  4. Two Types of Chemical Compounds • ionic: bond between anions (-) and cations (+) (electrons are donated) nonmetal—metal • molecular: (covalently bonded—electrons are shared) nonmetal—nonmetal • Metallic: electron “sea” allowing few electrons to be shared among many atoms metal—metal

  5. Monatomic Ions • Ions formed from a single atom • Groups 1 and 2 metals lose electrons to form cations • Groups 15, 16, and 17 gain electrons to form anions • Naming cations is very simple: identified by the element’s name K+ potassium cation Mg2+ magnesium cation • Naming anions: drop the ending to the element’s name and add –ium O2- oxide Cl- chloride

  6. Transition metals have variable charges!!!

  7. Stock System When naming ionic compounds and an element has multiple possible charges, the charge is given in roman numerals in () after the name of the metal Fe2+ iron (II) Fe3+ iron (III) Naming a binary ionic compound according to the stock system illustrated below. CuCl2

  8. Binary Ionic Compounds • Binary compounds: compounds composed of two elements • The total number of positives and negatives must be equal, resulting in an overall neutral charge Na Cl Mg Br2

  9. Writing chemical formulas for binary ionic compounds “crossing over”: a method of balancing charges between ions in an ionic compound • Write the symbols for the ions side by side. Write the cation (+) first! 2. Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other ion 3. Check to make sure the numbers are in the smallest possible ratio!

  10. Naming Binary Ionic Compounds -The nomenclature, or naming system, of binary ionic compounds involves combining the names of the compound’s positive and negative ions -the cation is ALWAYS written first!! -charges are ONLY given as part of the name if multiple charges are possible

  11. Practice Potassium and iodine Magnesium and chlorine Sodium and sulfur Sulfur and aluminum Nitrogen and aluminum

  12. More practice AgCl ZnO CaBr2 SrF2 BaO CaCl2

  13. Compounds containing polyatomic ions • Most polyatomic ions are oxyanions—polyatomic ions that contain oxygen • Some elements can combine with oxygen to form more than one type of oxyanion NO2- nitrite (fewer O atoms) NO3- nitrate SO32- sulfite (fewer O atoms) SO42- sulfate

  14. Sometimes an atom can form more than 2 oxyanions… Hypochlorite ClO- fewer O than –ite ion Chlorite ClO2- Chlorate ClO3- Perchlorate ClO4- one more O than –ate ion

  15. Practice Sodium iodide Calcium chloride Potassium sulfide Lithium nitrate Copper (II) sulfate Sodium carbonate Calcium nitrite Potassium perchlorate

  16. Practice AgO Ca(OH)2 KClO3 NH4OH Fe2(CrO4)3 KClO

  17. Naming Binary Molecular Compounds Unlike ionic compounds, molecular compounds are composed of individually bonded units, or molecules Two Systems: • Prefixes (“Old system”) • Stock system (uses oxidation numbers) NONMETAL—NONMETAL

  18. Examples CCl4 carbon tetrachloride (tetra: prefix for 4) CO2 carbon dioxide (di: prefix for 2) P4O10tetraphosphorusdecoxide (deca: prefix for 10)

  19. Prefixes Number Prefix 1 mono- 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca-

  20. Binary Compounds of N and O N2O dinitrogen monoxide NO nitrogen monoxide NO2 nitrogen dioxide N2O3 dinitrogen trioxide N2O4 dinitrogentetraoxide N2O5 dinitrogenpentoxide No prefix is used for the first atom if it is a single atom

  21. Practice SO3 ICl3 PBr5 Carbon tetraiodide Phosphorus trichloride Dinitrogen trioxide

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