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Chapter 3 Intro To the Periodic Table

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					Chapter 3: Intro To the Periodic Table
History
 1800’s- 60 known elements + their atomic
  masses
 1829 - Döbereiner’s Triads (groups of 3)
   Some elements grouped in 3’s by their
    properties
   Physical properties of the middle element usual
    about ½ way between those of the other 2
    elements.
   Ex: Halogen Triad: Cl, Br, I (see Table 3.1, p 87)
Döbereiner Triads
 Halogen Triad: Cl, Br, I


 Alkali Triad:
   Li = 7 g
   Na = ?
   K = 39 g


 Coinage Metals Triad: Cu , Au, Ag
History (cont.)
 1869- Dmitri Mendeleev noticed that
 properties of elements repeated in an
 orderly way when organized by atomic
 mass. This is periodicity.

 He put them in order from lightest to
 heaviest (atomic mass) & grouped them
 when properties repeated themselves. (see
 Table 3.3 on p 90 of text)
History, cont.
Even though Mendeleev couldn’t
 identify Zn, Si, and Ca, he was able
 to predict
    their existence and
    their behavior!
Modern Periodic Table
Elements placed in order of
 increasing atomic number.
Noble gases have been added
Synthetic elements too
Each period begins w/ a metal &
 ends w/ a noble gas (see p 92- 93)
Using the Periodic Table
(Review)
 Groups
  o Group # for Main Group Elements indicates
    the # of v.e-s
  o Elements in a group have similar chemical
    properties b/c the # of v.e-s is the same (AND
    VALENCE ELECTRONS DETERMINE
    CHEMICAL REACTIVITY!)
 Periods
  o Period # indicates the energy level of the v.e.-s
Using the Periodic Table, cont.
(New Info)
 Periods
  oEach period ends with a Noble Gas


 Each period ends with
 oa full s sublevel (___ v.e.-s) OR
 ofull s & p sublevels (___ v.e.-s)
Using the Periodic Table, cont.
Group Names
 oGroup #1: Alkali Metals
 oGroup #2: Alkaline Earth Metals
 o(Group #16: Chalcogens)
 oGroup #17: Halogens
 oGroup #18: Noble Gases
Physical States of the Elements
The P. Table shows the state of the
 elements at room temperature.
 oMost elements are solid
 oSome elements are gas (most on
  right side of P Table. Only H is on
  left.)
 o2 elements are liquid (Br & Hg)
                   3 Classes of the Elements:
                      Common Properties
                    Metals                      Nonmetals                Metalloids
Uses                Vehicles, jewelry, coins,   Abundant in nature-      Computer chips,
                    wires, computers            fuels, living tissue,
Examples            Na, Ca, Ti, Cr, Fe, Cu,     H, He, C, N, O, F, I     B, Si, Ge, As, Sb, Te,
                    Ag, Zn, Pt, U               (most are gases)         Po, At
Color               Silvery luster (shine)      Various
Conductive (heat    Very                        No                       Poor to fair
& electricity)
Malleable           Yes                         No-Brittle, when solid   Often brittle
Ductile             Yes                         No- “ “ “                No
Groups              1*-12, most of 13, +      H, 1 in Group 14           Groups 13-17, only
                    inner transition elements 2 in Group 15              1-2 elements in ea
                                              3 in Group 16              group
                                              4 in Group 17
                                              All of Group 18
# of v.e.-s         1, 2, 3, Sn & Pb (4 v.e.-   (4), (5), (6), 7 & 8     3-7
                    s), & Bi (5 v.e.-s)
Metalloids
 Metalloids are often called
  semiconductors.
 They conduct heat & electricity, but
  poorly
 This is good in computers b/c they
  don’t overheat.
 Doping is used to make them better
  conductors.
Metalloids & Doping
 Have an electron arrangement that keeps
 them from moving freely.
 Ex: each germanium atom (Ge) has 4 v.e.-s
  it shares with 4 neighboring Ge atoms.
 This creates a stable lattice, in which e-s are
  spaced evenly throughout the Ge, so they
  don’t move
Metalloids & Doping
“Doping”- If you place an
 occasional atom of another
 element, In or As, among the Ge
 atoms, you increase the
 movement of the e-s
 2 Types of Doping
 n-type: creates a
 shortage of e-s, in
 some areas, so
 they move to try
 to even out the
 charges

Indium has 3 v.e.-s, so
in the lattice, there are
“holes”- areas missing
an e-
                2 Types of Doping
p type: creates an
excess of e-s in
some areas, so they
move to try to even
out charges

				
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posted:1/23/2012
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