Lecture Periodic Table

Tom Lehrer periodic table song: 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.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). 2.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: