The Periodic Table

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Transcript of The Periodic Table

  • 1. The periodic table Presentation by Lisa Allen, Stonington High School

2. What does periodic mean? 3. Stanislao Cannizzaro

  • 1860 Presentation to Chemists
  • Demonstrated a reliable way to determine the atomic mass of an element
  • Every chemist who saw the presentation began doing experiments to find the atomic mass of an element.Before long, many atomic masses were known

4. Another dead chemist...

  • Dmitri Mendeleev
  • Born:8-Feb - 1834 Birthplace: Tobolsk, Siberia, Russia Died:2-Feb - 1907 Location of death:St. Petersburg, Russia Cause of death:Influenza

5. Dmitri Mendeleev - 1869

  • Sorted elements
  • Began withnew atomic masses
  • Saw PERIODIC PATTERNS of elements chemical properties.
  • Organized a chart by sorting elements
  • See p. 134, Holt Modern Chemistry

6. The original Periodic table 7. Sorting can be a powerful tool 8. A challenge at the start

  • Some elements needed to be placed slightly out of sequence to fit the periodic trends.
  • What is the thinking that allowed Mendeleev to place iodine AFTER tellurium on his chart?

9. Support for the structure of the periodic table

  • Some spaces existed, where elements should have been.Mendeleev (bravely) predicted the existence of 3 elements based on the spaces in his table.He predicted their properties, too.Those elements (Ge, Ga, Sc) were discovered within 15 years, validating his table.

10. Activity: Design a Periodic Table

  • Cut apart the elements on the sheet provided
  • Sort them first by mass, as Mendeleev did
  • Organize the Q values periodically
  • You should have trends in Q that are consistent along both vertical and horizontal axes
  • You may need to reorder a few elements by mass, as Mendeleev did

11. Assignment

  • Create a periodic table from the elements provided.Make a map of the table, or glue the cards onto a piece of paper.
  • Write a 6-8 sentence paragraph describing the structure of the table you have created, the decisions you made in the organization, and trends it demonstrates.
  • Due next class

12. Advantages you have over D.M.

  • Youknowthat theres some right answer, some validity to organizing these elements.
  • He had nothing but intuition to tell him that there is some reason for chemical periodicity.
  • DM had no noble gases.They are so similar in their state at room temperature and their lack of reactivity, that they are the easiest family of elements to identify.

13. Groups of the periodic table

  • Elements Mendeleev grouped by property share avalence electron configuration.
  • ns 1is the alkali metals.They are reactive, stored under oil in the dark, cut like taffy.
  • ns 2is alkaline earth metals.They are harder and denser than ns1, have higher MP
  • ns 2 np 5is the halogen family.
  • ns 2 np 6is the noble gas family.

14. Alkali metal properties

  • I apologize in advance for the pathetic tone of geeks trying to appeal to teens.This guy has cool toys.You just have to ignore his word choice, his haircut, and his little outfitsorry.Just dont say I didnt warn you!

15. Homework

  • Page 149, #2 and 3
  • Page 166, #2, 3, 4, 6, 8, 9, 13, 16
  • If you have not read chapter 5 in its entirety, please do so this weekend.Also, try the practice problems on pages 143, 146, and 148.These practice problems will not be collected.

16. Part Two: Periodic Properties Electronegativity Atomic radius Ionization energy Electron affinity 17. Electronegativity

  • Definition The ability of an atom to attract electrons in a bond.
  • For example, when forming H 2 O, the oxygen attracts the shared electrons much more strongly than the hydrogen, because it is more electronegative.This is why water is polar.It has a slightly negative end, where the oxygen is, and a slightly positive end, where the hydrogen is.

18. Images of water molecules: notice the charges! 19. Atomic Radius

  • Atomic radius: the size of an atom, usually established by dividing the distance between 2 bonded atoms by 2 (distance between nuclei of O 2 2)

20. What controls atomic size?

  • Effective nuclear charge, or z*
  • Number of energy levels

21. Other Periodic Properties

  • Electron affinity: The energy an atom gives off when it acquires an electron

22. Ionization energy

  • Definition: the amount of energy it takes to rip an electron off from an atom
  • Which elements would be easy to steal from?Which would be hard?What causes the difference?

Ionization , Acrylic on Canvas, Niall Higbee 23. Periodic trends assignment Electronegativity Atomic radius Ionization energy Electron affinity 24. What you will do:

  • Create a 3-D periodic table illustrating the trend in the property you have been assigned to study.
  • Create a 5+ slide power point presentation explaining thereasonfor the patterns, both down a group and across a period.Include pictures, as well as text.Save it to your own CD or USB flash drive.
  • Present your Power point to the class.
  • Explain, and handle questions from students and from me.
  • Write a paragraph on your trend individually in class.

25. Rubric for evaluating success Uh, can I call a lifeline on that? Difficulty explaining trend, or answering questions Answers demonstrate understanding. Answers refer to PP as well as to the 3-D table and demonstrate good understanding Handling Questions Nothing to hear! Difficult to hear, or hard to follow.Read presentation. Needs prompting to speak loudly enough to be heard.Good effort to communicate effectively. Audible, clear, no ummmm or uhhh, Easy to follow. Explanation Oh, yeah, I guess all the big ones are on one side, arent they? Understands trend, may not be able to explain why the trend exists. Understands trend, communicates reasons for trend Links trend to atomic structure, as well as to other periodic properties. Demonstrated understanding in written paragraph You mean on the computer? All text, mostly quotes from the book. Meets expectations for length, some visuals. Visually interesting, good explanationsPower point I was supposed to make a table?When? Key is missing, or table does not represent trend in 3-D Work is easy to interpret.Key is included. Table is creative, visually interesting, easy to interpret 3-D Table0 1 2 3 26. Issues we need to resolve...

  • How do we divide up the responsibility for the work so that nobody coasts, and nobody feels (s)he is carrying the group?
  • What role does self-assessment play in evaluating this?
  • How do you want to handle it if your group says one member didnt do anything?
  • How do you want to handle absentees?