The Periodic Table by a0D6zh7Q

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									The Periodic Table
               Unit 5
            Chapter 5
Ok, so now what?
   Recall that elements cannot be broken down
    any further.
   In the late 1800’s, we had “discovered” about
    60 elements.
   We had no idea of the structure of atoms.
   Many scientists attempted to put order to the
    rapidly expanding list of elements.
Off to the Newlands…

                    Arranged known elements in a
                     table by atomic mass in 1863.
                    Noticed a repeating pattern every
                     8th element in 1865.
                    Law of Octaves – chemical
                     properties repeat every 8
                     elements.
                    Was laughed at by peers.
 John Newlands
  (1837-1898)
Newland’s Flaw
   Knew nothing of subatomic particles
   His table mixed some obviously different elements
    (like oxygen and iron)
The Mad Russian

                       Produced a more orderly table
                        independent of Newlands’ work
                        in 1869 (also used atomic mass).
                       Left blanks for yet-undiscovered
                        elements.
                       Predicted properties of Ga, Sc,
                        and Ge (which were discovered
 Dmitri Mendeleev       in 1875, 1877, & 1886).
   (1834-1907)         Credited with developing the
                        Periodic Table.
Russian Roulette
   Mendeleev’s table had a few
    problems.
   Based on atomic weight, he
    had to switch a few elements
    (e.g. Tellurium and Iodine) to
    keep the reactivities in order.
   Many believed he predicted too
    many elements (we had 63
    already!!!).
   Still, this is what we used for
    half a century.
45 Years Later…
                   Rearranged table according to
                    electronic charge in 1914.
                       Became the # of protons after 1918.
                   Noticed his new table had spots for
                    #’s 43, 61, 72, & 75.
                   Produced the modern periodic table
                    we know today.
                   Enlisted in the army’s Royal
Henry Moseley
(1887 – 1915)       Engineers when WWI broke out.
Moseley’s New Periodic Table
   Gave experimental meaning to atomic
    number.
   Gave reason for Tellurium and Iodine
    being switched.
   Moseley’s technique easily separated
    rare earth metals.
       Plagued chemists for years and years.
  Used to predict how many elements
   remained between others.
(e.g. 13 elements between La and Lu)
Moseley’s Lost Nobel
   Many thought he should have won Nobel Prize.
   It’s only given to the living…he was shot in the head
    by a sniper in Gallipoli.
   Bohr (1962): "You see actually the Rutherford work
    [the nuclear atom] was not taken seriously. We
    cannot understand today, but it was not taken
    seriously at all. There was no mention of it any
    place. The great change came from Moseley."
   Moseley’s promising career was cut short.
   Because of this, the British barred scientists from
    enlisting for combat.
The Modern Periodic Table
   A chart of the elements showing the
    repeating pattern of their properties.
   Elements are arranged in rows and columns
    by increasing atomic number.
   The atomic number increases by 1 between
    each element.
Rows & Columns
                                  Group 18
                               The Noble Gases
   A vertical column is
    called a group or family                                  He
    because…          Li Be    B    C      N      O       F   Ne
   Elements in columns                                       Ar
    have similar properties.
                                       Period 2               Kr
   A horizontal row of            (Not similar at all)

    elements is called a                                      Xe
    Period because…                                           Rn
   Properties repeat
    periodically
Info on the Table
   Periodic Tables include the
    chemical symbols of the            2
    elements.
   These are 1 or 2 letter
                                           He
    abbreviations for the elements.        Helium
   The table is arranged by atomic
    number
   This is the number of protons in
    the nucleus.
More Stuff
   The tables also include the atomic weight.
   This is the average mass of an atom of the
    element.

                   2              The Atomic Weight
                       He          varies depending
                                    upon where you
                    4.002602       find your sample!
                       Helium
Elements Everywhere
   Based on increasing number of protons, we
    now have a complete periodic table.
   Will not find any lower elements, can only go
    up (118 so far).
   We can create new elements by smashing
    smaller atoms together:

    48           249
      Ca         294 Cf
    20           118 Uuo
                  98

                                           3 Neutrons
Division of Labor
   Different types of elements are found on
    different parts of the Periodic Table:
   Metals to the left (majority of the elements).
   Nonmetals to the right (10 elements).
   Noble Gases (Group 18)
   Metalloids found on a “staircase” dividing
    metals and nonmetals (7 elements).
   Lanthanoids & Actinoids (metals) added to
    bottom to make table manageable.
Metals are
   Lustrous (shiny)
   Malleable (can be pounded into
    thin sheets)
   Ductile (can be pulled into
    wires)
   Conductive
       Heat and electricity
   Form solid oxides when burned.
   Tend to react with acids to form
    Hydrogen gas.
Nonmetals have a
   Wide range of properties
   They tend to:
   Be Dull
   Brittle (when solid)
   & Insulators
   They form gaseous oxides
   Do not react much with acids
   Have lower melting & boiling
    points.                        Bromine
Metalloids
   Also called “semi-metals” or
    “staircase elements.”
   Combination of properties of
    metals and nonmetals.
   Boron, Silicon, Germanium,
    Arsenic, Antimony, Tellurium,
    & Polonium
   Many exhibit semi-conducting
    behavior.
Semiconductors
   Conduct electricity better than insulators, but
    worse than conductors.
   Conductivity usually increases with an
    increase in temperature.
   Semiconductors are used extensively in
    computers, most notably Silicon.
   Properties can be modified by adding
    impurities – this is called “doping.”
s-Block Elements
   At least 1 e- in s orbital (nsx)
   Groups 1 & 2
       Alkali Metals
       Alkaline Earth Metals
   Reactivity increases as you go down
   All are metals, except H & He
   Helium is technically an s-block, but placed
    with Noble Gases b/c of reactivity (or lack of)
p-Block Elements
   At least 1 e- in p orbital (npx)
   Groups 13-18
   The nonmetals are at the top and they
    gradually transition into metals
   All nonmetals and metalloids are p-block
    elements (excl H & He)
   Only a few p-Block metals (Al, Ga, In, Sn, Tl,
    Pb, Bi)
d-Block Elements
   At least 1 e- in d orbital (ndx)
   Groups 3-12
   Called the Transition Metals
   Very little similarities within the group
   All are metals &
   Most form ions with multiple charges.
f-Block Elements
   At least 1 e- in f orbital (nfx)
   These are the oddballs
       Lanthanoids start with #57, La
       Actinoids start with #89, Ac
   The groups are NOT similar up & down
   All of them are metals
   Lanthanoids (4f) are natural, while most
    Actinoids (5f) are man-made
Why are they there?!?
   The f-block elements are placed at the
    bottom of the periodic table to make the table
    manageable.
   They should fit in between the s-block and d-
    block elements, but
   That would make the table too long:
H                                                  He




    s                                          p
                                    d
                 f

								
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