The Periodic Table

1. The Periodic Table The Ultimate Cheat-Sheet

2. Elementary My Dear Watson…. • Elements are distinguished by the number of protons • Each element has unique properties • How are they arranged? Is there a pattern?

4. The “Original”

5. Why Do We Need a Periodic Table? • By 1700, only 13 elements were known • The rate of discovery increased in the 18th century (Davy, Lavoisier, Priestly) • But how could scientists know an element was “new?” • Chemists needed a way to organize the elements

6. How Was It Developed? • In 1829, Dobereiner published a classification system using triads • Triads are groups of 3 elements with similar properties • But, not all elements could be grouped into triads

7. Lothar Meyer • In 1864, Lothar Meyer published an early version of the periodic table • It contained 28 elements classified into 6 families by their valence (combining power) • This was the first time that elements had been grouped and ordered according to their valence. • Work on organizing the elements by atomic weight had hitherto been stymied by inaccurate measurements of the atomic weights.

8. de Chancourtois One of the first to notice periodicity In 1862 developed a cylindrical design Ignored due to “geological terms”

9. How Was It Developed…. • In 1865, Newlands classified elements into 11 groups • Noticed that many groups differed by “8” • He called this his “Law of Octaves”

10. Development • Other systems were explored… • In 1869, Dmitri Mendeleev proposed his periodic table • He played “chemical solitaire” on the train • There were 60 elements to organize 1834-1907

12. How Did Mendeleev Do It? • He organized the elements by increasing atomic mass and “combining power” • He left a space in his table if an element was unknown • In time, those spaces were filled in with elements that matched his predictions

13. Elements’ Properties are Predicted O’Connor Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 119,

14. Mendeleev • Some people consider Meyer and Mendeleev the co-creators of the periodic table • Most agree that Mendeleev's accurate prediction of the qualities of what he called eka-silicon (germanium), eka-aluminium (gallium) and eka-boron (scandium) qualifies him for deserving the majority of the credit for studies

15. Mendeleev did not know the structure of atoms and that the number of protons was unique for each element • Now the periodic table is arranged by increasing atomic number

16. The Modern Periodic Table • Is an organized display of elements • Is arranged so that elements with similar properties fall into the same group • Is used to predict the behavior of elements The “Noble Gases” don’t easily react with other elements.

17. Rows of the Periodic Table • Rows of the PT are called “periods.” • All of the elements in a period have the same number of energy levels for their valence (s & p) electrons

18. K and Ca are similar K and Kr are very different Periods (cont.) • Elements close to each other in the same period are more similar than those further away.

19. So… • Properties of the elements within a period change as we move across a period from left to right • The pattern of properties within a period repeats as we move from one period to the next

20. The Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties

22. Regions of the PT

23. 1) Metals The largest region of the PT ~ 80%

24. Sodium metal Copper wire Gold charm Properties of Metals • Excellent conductors of heat and electricity • Usually lustrous, ductile, and malleable.

25. 2) Nonmetals The second largest region of the PT

26. Chlorine gas Graphite Diamond Properties of Nonmetals • Poor conductors of heat and electricity • Most are gases or brittle solids at room temperature.

27. 3) Metalloids • Have some properties of metals and some of nonmetals • Silicon is useful in computers because they conduct electricity “moderately” • Semi-conductors

28. Other Uses of Metalloids • Lasers • Infrared sensors • Alloys • Glass products • Added Impurities

29. The Elements at the Bottom These are the lanthanides and actinides Glenn Seaborg “moved” these

30. Special Groups of Elements • Group 1A – the Alkali Metals • The name alkali comes from the Arabic al aqali, meaning “the ashes.” • Wood ashes are rich in compounds containing sodium and potassium • Group 2A – the Alkaline Earth Metals • Group 7A – the Halogens • Literally means “salt former”

31. The Representative Elements • These are the elements in Groups 1A – 7A • They represent a wide range of properties • Metals, nonmetals, and metalloids • Solids, liquid (Br), and gases • The highest level s & p orbitals are NOT filled

32. Examples • Electron configurations for Group 1A • Electron configurations for Group 4A

33. Group 1A Group 4A Group Number and e- Number For any representative element, its group number equals the number of electrons in the highest occupied energy level (valence electrons).

34. Noble Gases • NOT considered representative elements • Unreactive • Uses: Krypton is mixed with Argon in fluorescent lights (also to render Superman inert) Neon is used for signs Helium is used in weather and toy balloons

35. What About The “Ones in the Middle” • These have different letter designations, depending on the table • These are also called • Transition metals • Inner transition metals

36. Transition Metals • The highest occupied s sublevel and a nearby d sublevel contain electrons • These elements are also called d -block elements

37. The Inner Transition Metals • AKA: the lanthanides and actinides. • The highest occupied s sublevel and a nearby f sublevel generally contain electrons.

38. f-orbitals

39. Blocks of Elements

40. Rare Earth Elements • Scandium, Yttrium, Lanthanum, and Cerium through Lutetium • Used in electronics • Thulium (Tm) – lasers & x-rays • Neodymium (Nd) - magnets • Not rare – hard to separate • Elements very similar • Charges are 3+

41. The Racetrack Design