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The Periodic Table


Development of the Periodic Table
    A.  provided order to increase number of known elements their properties
    B.  from 1700s to 1800s the number of known elements doubled
    C.  forerunners of the periodic table
        1.  Dobereiner, 1800s
              a.  classified elements in groups of three
              b.  called triads
              c.  ex. Li, Na, and K
              d.  elements have similar properties
              e.  middle elements average of the first and third - density, mass
        2.  Newlands, 1865
              a.  62 known elements
              b.  arranged elements based on increasing atomic mass
              c.  noticed the eighth element was like the first, ninth like the second so on.
              d.  pattern repeated every eighth element
              e.  called the law of octaves (musical scale)
        3.  Mendeleev and Meyer, 1869
              a.  published almost identical tables
              b.  Mendeleev was first and was better demonstrated
              c.  noticed the same repetition in element properties
              d.  arranged elements in columns having similar properties
              e.  produced the first periodic table
              f.  Mendeleev's favored
                  1.  suggested masses of certain elements were wrong
                  2.  left gaps in the table in order to keep element in columns with similar properties
                  3.  gaps were due to undiscovered elements
                  4.  was able to predicted the properties on the knowns
              g.  ex. germanium
              h.  saw the correct pattern but for the wrong reason
        4.  the periodic law
              a.  Mendeleev's was not perfect
              b.  some elements were out of place
              c. lacked critical property of elements - atomic number
              d.  atomic number determined by Moseley
              e.  today's periodic table arrangement based on the atomic number
              f. 
periodic law - the physical and chemical properties are periodic function their atomic number


II  Reading the Periodic Table
    A.  organizing the squares
        1.  each element represented by blocks
        2.  each contains basic information: name, symbol, atomic number, atomic mass, partial electron configuration
        3.  shape based on the periodic law
        4.  elements with similar properties in vertical  (18) columns called groups or families
        5.  horizontal rows (7) called periods
    B.  labeling and naming groups
        1.  3 systems
              a.  Roman numerals with letters A and B
              b.  Arabic number with letters A and B
              c.  Arabic numbers only
        2.  family names
              a.  1A - alkali family
              b.  2A - alkaline family
              c.  7A - halogens
              d.  8A - noble gases
              e.  others identified by name of the element listed first in the column - ex. carbon family
              f.  hydrogen - unique family of its own
    C.  metals, nonmetals, and semimetals
        1.  metals
              a.  most elements
              b.  properties
                  1.  have luster
                  2.  good conductors: heat and electricity
                  3.  mostly solid at room temperature
                  4.  malleable
                  5. ductile
        2.  nonmetals

              a.  properties
                  1.  lack luster
                  2.  poor conductors of heat and electricity
                  3.  not malleable or ductile
                  4.  many gases at room temperature
              b.  properties vary widely: color, hardness
        3.  semimetals - metalloids
              a.  have some metallic properties and some nonmetallic
              b.  intermediate between the two
    D.  electron configuration and the periodic table
        1.  shape of the table, element grouping, and rows related to electrons configuration
        2.  all elements in group 1A have one outer electron (s)
        3.  outer electrons or valence electrons responsible for chemical behavior         
        4.  elements' similar properties due to similar configurations
        5.  principal quantum number for the s orbitals of the 1A group is the same as the period number
              period      1A
                  1          1s1
                  2          2s1
                  3          3 s1
    E.  the s-, p-, d-, and f-block elements
        1.  shape of the table determined by electron configuration
        2.  s-blocks
              a.  groups 1A and 2A
              b.  valence electrons s orbitals 
                  1. 1A   -  1 valence electron   
                  2. 2A   -  2 valence electrons
              c.  two groups because s holds only two electrons
        3.  p-block
              a.  valence fill p orbitals
              b.  3A - 8A
              c.  last sublevel in the electron configuration p1 to p6
              d.  first period no p-block because no p orbital
              e. p-block 6 elements wide because p orbital holds 6 electrons
        4.  d-block
              a.  middle of table
              b.  holds 10 electrons contains 10 elements
              c.  first d orbital in the fourth period
        5.  f-block
              a.  first f orbital in the sixth period
              b.  14 electrons - 14 elements
              c.  do not go from f1 to f14
        6.  periodic table
              a.  period 1 - s-block
              b.  periods 2 and 3 - s and p blocks
              c.  periods 4 and 5 - s, p, and d blocks
              d.  periods 6 and 7 - s, p, d, and f blocks
              e.  pattern determined by the principles of quantum theory
              f.  shape of periodic table due to the filling order
              g.  names
                  1.  s and p block elements - representative elements
                  2.  d- block - transitional elements
                  3.  f-block - inner transitional elements


III  Periodic Trends
    A.  predictable changes of properties as you move through the periodic table
    B.  atomic radius
        1.  center to outer most electrons
        2.  estimate
        3.  top to bottom - radius increases - more energy levels
        4.  left to right - decreases - more protons greater nuclear attraction
    C.  ionic size
        1.  lose electrons ions (+) become smaller
              a.  fewer orbitals or levels
              b.  reduced repulsive forces between remaining electrons
              c.  pulled closer to the nucleus
        2.  gain electrons:  ions (-) become larger
              a.  increases repulsive force
              b.  electrons move away from each other
        3.  ion charges
              a.  Group ions - same charge
              b.  left to right
                1.  period 1A = 1+
                2.  period 2A= 2+
                3.  period 3A = 3+
                4.  period 4A = 4+
                5.  period 5A = 3- 
                6.  period 6A = 2-
                7.  period 7A = 3-
        4.  ionization energy
              a.  energy needed to remove an electron from an atom
              b.  reflects on the strength of attraction an atom has for outer electrons
              c.  top to bottom - decreases
              d.  left to right - increases
              e.  opposite to atomic size trend
               f.  additional electrons removed with increased energy needs
              g.  significant increase in ionization energy values when an atom reaches noble gas configuration:
                                  Mg         [Ne] 3s2   needs   738 Kj;  1450 Kj
                                  Mg 2+    [Ne]          needs 7730 Kj
        5.  electron affinity
              a.  energy change when atoms gain an electron
              b.  measure of attraction for additional electrons
              c.  values usually negative - indicates a releases of energy
              d.  general rule: nonmetals more electron affinity than metals
              e. exception - noble gases
        6.  octet rule:  atoms tend to lose, gain, or share electrons in order to obtain the noble gas configuration
               (8 valence electrons) exception - first energy level (2 valence electrons)
        7.  Electronegativity
              a.  ability to attract electrons
              b.  no units
              c.  highest value - fluorine  lowest value  - cesium and francium
              d.  related to both ionization energy and electron affinity
              e.  trend similar to ionization energy
                  1.  top to bottom - decreases
                  2.  left to right - increases



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