Chemistry 20 – Elements_ Compounds and Nomenclature by malj

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									                   Chemistry 20 – Unit 3
          Elements, Compounds and Nomenclature
   the term “nomenclature” refers to “naming”
   chemical nomenclature is the organized system
    chemists use to name substances and write their
    chemical formulas
   when writing any formula for any substance we
    first assume that the substance exists on its own, at
    room temperature
   if special conditions exist, states of matter are
    adjusted
Naming Pure Elements
Metals
   when naming metals, we simply state the
    elemental name given on the periodic table
   when writing the formula for any pure metal we
    simply write the elemental symbol (no subscripts)
   inclusion of states of matter is very important, so
    we must always indicate a solid state, the exception
    being mercury, Hg(l)




Chemistry 20 – Unit 3                  Page 1     Overhead Notes
Elements, Compounds and Nomenclature
Nonmetals
   when naming nonmetals, we simply state the
    elemental name given on the periodic table
   when writing the formula for any pure nonmetal
    we write the elemental symbol with subscripts for
    some of the nonmetals, because we must also be
    aware of how it exists at room temperature
   for most nonmetals, you’ve just got to memorize
    their formulas and their natural states of matter
   all nobles gases are monatomic: He(g) , Ne(g) , Ar(g) ,
    Kr(g) , Xe(g) , Rn(g)
   diatomic elements include:
     nitrogen – N2(g)

     oxygen – O2(g)

     all halogens: fluorine – F2(g)

                      chlorine – Cl2(g)
                      bromine – Br2(l)
                      iodine – I2(s)
                      astatine – At2(s)
   polyatomic elements include:
     phosphorous – P4(s)

     sulfur – S8(s)

   all other nonmetals are monatomic and solid,
    except bromine




Chemistry 20 – Unit 3                  Page 2       Overhead Notes
Elements, Compounds and Nomenclature
Naming Compounds
   a compound is a pure substance made by combining
    at least two different elements in a specific ratio
Ionic Compounds
   an ionic compound is formed by taking one
    metallic ion and combining it with one
    nonmetallic ion or a complex ion
Binary Ionic Compounds
   only one metallic ion and one nonmetallic ion are
    combined
Process for Creating the Formula:
         - find the elements
         - list their ions
         - place positive ions (cations) first, followed by
           negative ions (anions)
         - criss-cross their charges to create the correct
           ratio of each element and simplify charges
           (reduce)
         - the state of matter for all ionic compounds is
           solid




Chemistry 20 – Unit 3                  Page 3        Overhead Notes
Elements, Compounds and Nomenclature
Naming Ionic Compounds
   the first element gets its normal elemental name
    as found on the periodic table
   the second element’s name has an “ide” ending
    (regardless of the ratios found in the formula)
Examples:
             sodium and chlorine
              Na+           and        Cl –
                      Na + Cl –
                     Na –1 Cl +1
                       NaCl (one’s are ignored)
                       NaCl(s)
                   sodium chloride
             magesium and iodine
              Mg 2+ and I –
                   Mg 2+ I –
                  Mg –1 I 2+
                    MgI2
                    MgI2(s)
              magnesium iodide




Chemistry 20 – Unit 3                         Page 4   Overhead Notes
Elements, Compounds and Nomenclature
              oxygen and aluminum
              Al 3+ and O 2–
                   Al 3+ O 2–
                   Al –2 O +3
                    Al2O3
                   Al2O3(s)
              aluminum oxide
             oxygen and calcium
              Ca 2+ and O 2–
                  Ca 2+ O 2–
                  Ca –2 O +2
                   Ca2O2
              *note: subscripts are simplified for
                     ionic compounds
                    CaO
                    CaO(s)
               calcium oxide




Chemistry 20 – Unit 3                  Page 5        Overhead Notes
Elements, Compounds and Nomenclature
Creating the Formula and Naming Ionic
Compounds Using Complex Ions
   when a simple positive ion is combined with a
    complex ion the process is as follows:
     list both positive and negative ions

     combine both

     use brackets for the complex ion

     criss-cross their charges

     simplify subscripts

   when naming the compound, use the normal first
    name for the metallic ion and copy the given name
    of the complex ion, which is found in the complex
    ion table
    Examples:
        calcium and hydroxide
                   Ca 2+ and OH –
                   Ca 2+ and (OH) –
                    Ca –1 (OH) 2+
                     Ca1(OH)2
             since 1’s are not required
                  Ca(OH)2(s)
             note that if a 1 should appear after the
              brackets, the brackets are not required



Chemistry 20 – Unit 3                  Page 6            Overhead Notes
Elements, Compounds and Nomenclature
Naming Ionic Compounds Using Multiple Ion
Charges
   some metallic ions have more than one charge
   for example, iron has Fe2+ and Fe3+
   in these cases it is necessary to actually state which
    ion is being used
   Roman numerals are used after each multiple-
    charged ion
    Example
                             iron and oxygen
                             Fe2+ and O2–
                             FeO(s) named iron (II) oxide
                                      or
                                3+
                             Fe and O2–
                             Fe2O3(s) named iron (III) oxide
   some tables may use old, “classical” names that
    end with “ic” or “ous”
   “ic” ending is for the ion that has the greater
    charge
    Example
         Fe3+ is also called ferric
         Fe2+ is also called ferrous
         FeO(s) is also called ferrous oxide
         Fe2O3(s) is also called ferric oxide


Chemistry 20 – Unit 3                    Page 7                Overhead Notes
Elements, Compounds and Nomenclature
Hydrated Compounds
   some compounds have a strange-looking formula
    which has water added at the end, such as
    CuSO4 5 H2O(s)
   these are still ionic compounds and exist as solids
    at room temperature
   the only thing we have to do is to state how many
    waters are involved
   so, for CuSO4  5 H2O(s) , the first part is named as
    copper (II) sulfate and then we add that there are
    5 waters
   the Latin prefix for 5 is penta and water is called
    hydrate
   the name becomes copper (II) sulfate pentahydrate

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




Chemistry 20 – Unit 3                  Page 8           Overhead Notes
Elements, Compounds and Nomenclature
Naming Molecular Compounds
   molecular compounds are formed by combining
    nonmetallic elements
   when these elements are combined they may form
    more than one compound
   carbon and oxygen may combine to form CO(g) or
    CO2(g)
   nitrogen and oxygen may combine to form NO(g) or
    NO2(g) or N2O4(g)
   note that subscripts are not simplified and another
    naming system is used
    Example
             CO2(g) is made from carbon and oxygen
             the first element gets the normal name
             the second element gets and “ide” ending
             now we must state how many of each element
              is being used by inserting prefixes before
              each element name
             there is one carbon (monocarbon) and two
              oxygens (dioxide)
             if the first element is a “mono” the prefix is
              ignored but is used for the second element
             NO(g) is nitrogen monoxide
             NO2(g) is nitrogen dioxide
             N2O4(g) is dinitrogen tetroxide


Chemistry 20 – Unit 3                  Page 9         Overhead Notes
Elements, Compounds and Nomenclature
   there is no general rule for determining states of
    matter
   each molecular compound has its own
    characteristic state of matter at room temperature
    and these are learned as you go along
   some molecular compounds have classical names
    that have no logic involved in their naming system
   these we just memorize
    Examples
         H2O(l) is water
         NH3(g) is ammonia
         O3(g) is ozone
         CH4(g) is methane
         C6H12O6(s) is glucose
         C12H22O11(s) is sucrose
         CH3OH(g) is methanol
         C2H5OH(l) is ethanol
         H2O2(l) is hydrogen peroxide
         H2S(g) is hydrogen sulfide




Chemistry 20 – Unit 3                  Page 10   Overhead Notes
Elements, Compounds and Nomenclature
Hydrogen Compounds
        hydrogen compounds are those which contain a
         hydrogen at the beginning of the chemical
         formula and are dissolved in water (aqueous)
          Examples: HCl(g) , HNO3(aq)

        hydrogen bonds covalently (shares electrons) to
         nonmetals to form a molecular compound
         which may be any state of matter, depending on
         the species being formed
        most hydrogen compounds are named as acids
        the only exceptions to this rule are the following
         pure substances
          HCl(g) – hydrogen chloride

          H2S(g) – hydrogen sulfide

          HCN(g) – hydrogen cyanide

        when hydrogen compounds dissolve in water
         they form acidic solutions
          HCl(g) is bubbled into water to form a solution

           called hydrochloric acid




Chemistry 20 – Unit 3                  Page 11       Overhead Notes
Elements, Compounds and Nomenclature
Properties of Acids
             turns litmus indicator red
             tastes sour
             neutralizes bases
             conducts an electrical current
             pH is lower than 7
Naming Acids
Naming acids is easy if we follow this table:
        hydrogen ___ide becomes hydro___ic acid
        hydrogen ___ate becomes ________ic acid
        hydrogen ___ite becomes ________ous acid

Examples: Name the following acids.
   HF(aq) – the normal name given to this chemical is
    hydrogen fluoride, therefore, hydrogen fluoride
    becomes hydrofluoric acid
   HNO3(aq) – the normal name given to this chemical
    is hydrogen nitrate, therefore, hydrogen nitrate
    becomes nitric acid
   HNO2(aq) – the normal name given to this chemical
    is hydrogen nitrite, therefore, hydrogen nitrite
    becomes nitrous acid
We can read the table backwards to write out the
chemical formula of a given acid name.


Chemistry 20 – Unit 3                  Page 12   Overhead Notes
Elements, Compounds and Nomenclature
Example: Give the chemical formula for
         hydrosilicic acid.
   the acid name came from hydrogen silicate,
    therefore the formula must be H2SiO3(s)
   now change states to give the acid formula,
    H2SiO3(aq)
Classification of Acids
Binary Acids: contain a hydrogen and one other
              kind of atom
         Example: HCl(aq)

Oxo Acids: contain a hydrogen, an oxygen and one
           other kind of atom

         Example: HNO3(aq)




Chemistry 20 – Unit 3                  Page 13    Overhead Notes
Elements, Compounds and Nomenclature

								
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