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Lecture Periodic Table
Tom Lehrer periodic table song:
http://www.youtube.com/watch?v=SmwlzwGMMwc
Tell me something you did not know about the
periodic table before your reading.
What is something you thought was cool/unique
about it?
What is periodic?
What is periodic about the table?
1.
2.
Developed in the 1870’s by Mendeleyev with an
increasing atomic # (# protons).
Increasing Atomic mass would be incorrect, why?
because of the isotopes of atoms (different masses).
Organized and read like reading a book:
across and
down
-Arranged in periods (rows) by increasing atomic #
(what is at the end of a sentence ?)
-labeled by their period # ?
-each period indicates the number e- shells of the
element
-what are the most # shells for any atom ?
-each period’s elements have the same # electron
shells
A. Periodicity: the repeating pattern of the
chart (called periodic)
is reflected in the different periods
1. shows a repeating pattern of chemical
reactivity from period to period
-due to repeating:
valence e- # and
oxidation #
-ie: melting and boiling points:
both reflect strength of forces between
their molecules:
strongest when valence shells are half
empty (middle of periodic table)
2. diameter of atoms reduces across periods
3. energy needed to remove valence e- increases
across periods
Non-periodic atomic number
3. Also arranged in groups (or families) (columns: like
columns which hold up things: vertical).
labeled by: 1) group #, or
2) oxidation #, or
3) element at the top
Elements in the same group have:
A. similar characteristic properties: bp/fp/sp heat
B. same # electrons in the valence shell
C. same oxidation #: charge after octet rule applied
4. Zig-zag line between B-Al and Po-At separates metals
(80% chart) on the left from non-metals on the right
5. The most reactive:
A. metals: bottom left (Fr), easily gain or lose e-: thus
good electricity and heat conductors
B. non-metals: top right (F), e- held tightly,
tend not to lose e-: good electricity resistors
6. Far right (group 18) is the group of noble gases.
These are inert, non reactive: because
the valence shell is full (oxidation # is 0)
7. Transition metals: middle of chart: groups Sc  Zn,
can have different oxidation #’s depending on the
chemicals and environments they are reacting with
8. Some elements are synthetic: human made.
First is Tc (technetium: greek for artificial) and all
elements > 92 (plus 61)
9. Halogens: Fluorine group: 17, very reactive due to -1
oxidation # (7 e- in valence shell):
combine w/ alkali metals to form salts
10. Alkali metals: Hydrogen group: 1, very reactive due
to +1 oxidation # (1e- in the valence shell)
11. Alkaline earth metals (group 2): 2 e- in
valence shell: very reactive
12. Metalloids: have properties of both metals
and non-metals: along the zig-zag line
13. Decreasing atom size going to the right of
each period:
increasing + charged nucleus pulls -e closer
together (opposites attract)
Key point:
periodicity of the chart is due to a
repeating trend of oxidation numbers
toward a formation of a stable configuration
circular periodic tables: