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Trends in the Periodic Chart

Trends in the Periodic Chart. …position  electrons  physical and chemical properties…. …the position indicates physical and chemical properties of elements!. There are two effects:. Attraction— Shielding—. There are two effects:. Attraction— as Z increases, attraction increases BUT

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Trends in the Periodic Chart

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  1. Trends in the Periodic Chart …position electronsphysical and chemical properties…

  2. …the positionindicatesphysical and chemical properties of elements!

  3. There are two effects: • Attraction— • Shielding—

  4. There are two effects: • Attraction—as Z increases, attraction increases BUT • Shielding—as Z increases, shielding increases: --a little bit with each electron in the same period --in a great jump as you start the next period

  5. Shielding • Shielding is the weakening of attraction due to electrons interfering with the attraction of the nucleus • Shielding increases a little as you go across a period (not as much as attraction) • Shielding jumps tremendously as you start a new energy level

  6. Periodic trends

  7. Simple Valence electrons • The representative (tall) columns represent the number of valence electrons • Transition elements have only two valence electrons, but have a part-filled d sublevel

  8. How many valence electrons?

  9. Simple Electron configurations

  10. EC ends in…

  11. EC ends in… ns1 ns2 * * *

  12. EC ends in… * * * ns2(n-1)d? ns2(n-2)f14(n-1)d? ns2(n-2)f?

  13. EC ends in… * ns2np? * * ns2(n-1)d10np? ns2 (n-2)f14 (n-1)d10np?

  14. Simple Ionization pattern • Metals have -only a few valence electrons -lose these electrons to empty their valence level -form positive ions

  15. Simple Ionization pattern • Non-metals have -more valence electrons -gain electrons to fill valence level -form negative ions

  16. What is the charge on the ion?

  17. Medium Atomic size • In a column, a lower row indicates an extra energy level • Outer energy levels are larger (due to shielding) • The largest atom in a column is the bottom element

  18. Medium Ionization energy

  19. Medium • Ionization energy— the energy required to remove an electron X + IE X+ + e- • Outer energy levels are farther from the nucleus • It is easier to remove an electron from a larger energy level • The lowest ionization energy is at the bottom of the column

  20. Medium Electronegativity —the attraction an atom has for a shared pair of electrons • See previous—the highest electronegativity is at the top

  21. Medium Electron affinity —the attraction an atom has for an electron from outside X + e-X- + EA • See previous—the highest electron affinity is at the top

  22. One moment… As you go across a row, you get more protons in the nucleus • They attract the electrons better • Each energy level gets smaller

  23. Hard • Atoms get smaller as you go across a row • Ionization energy gets larger • Electronegativity gets larger • Electron affinity gets larger --All because there are more protons— Z increases faster than shielding in a period

  24. Recap • Atomic size • INCREASES as you go down and left

  25. Recap • Electronegativity, ionization energy, and electron affinity • INCREASE as you go up and right

  26. Pop Quiz • Which element on the entire periodic chart is the largest? • Smallest? • Which element on the entire periodic chart has the largest IE? • Smallest?

  27. Pop Quiz • Which element on the entire periodic chart has the largest e-negativity? • Smallest? • Which element on the entire periodic chart has the largest EA? • Smallest?

  28. Pop Quiz • Who’s your favorite pop star?

  29. Which has the greatest / least: Size, IE, EA, e-neg? F C I Sn

  30. The diagonal effect • Of the previous four elements, the ones in the same row and column are easy, right? • What can you say about carbon and iodine? • Try this– they might be just about the same!

  31. The metal/nonmetal line Diagonal effect! (probably electron affinity)

  32. Hard (cont’d) Ionic radius Negative ions are (way) larger than their atom Positive ions are (way) smaller than their atom

  33. Which has the largest / smallest ion? Be Li Ca K

  34. Which has the smallest / largest ion? S Mg Te Sr

  35. Which has the smallest / largest ion? +2 -2 +2 -2 S Mg Te Sr

  36. Hard (cont’d) Second and third ionizations • If you ionize an atom, you make a (+) ion • It’s harder to ionize it again • It gets way harder after you empty the valence level

  37. Hard (cont’d) Second and third ionizations • If you ionize an atom, you make a (+) ion • It’s harder to ionize it again • It gets way harder after you empty the valence level Why?

  38. Hard (cont’d) • First, second, and third ionization energies X + IEX+1 + e- X+1 + IE2X+2 + e- X+2 + IE3X+3 + e-

  39. Disclaimers • Noble gasses have no electronegativity—they don’t share electrons • Noble gasses have no electron affinity—they don’t gain electrons • Most metals have no electron affinity—they don’t gain electrons

  40. Ionization Energies in kJ/mol • 1 2 3 4 5 H 1312 He 2372 5250 Li 520 7297 11810 Be 899 1757 14845 21000 B 800 2426 3659 25020 32820 C 1086 2352 4619 6221 37820 N 1402 2855 4576 7473 9442 O 1314 3388 5296 7467 10987 F 1680 3375 6045 8408 11020 Ne 2080 3963 6130 9361 12180 Na 496 4563 6913 9541 13350 Mg 737 1450 7731 10545 13627

  41. Ionization Energies in kJ/mol • 1 2 3 4 5 H 1312 He 2372 5250 Li 520 7297 11810 Be 899 1757 14845 21000 B 800 2426 3659 25020 32820 C 1086 2352 4619 6221 37820 N 1402 2855 4576 7473 9442 O 1314 3388 5296 7467 10987 F 1680 3375 6045 8408 11020 Ne 2080 3963 6130 9361 12180 Na 496 4563 6913 9541 13350 Mg 737 1450 7731 10545 13627

  42. Electron Affinity*, Electronegativity*, Ionization energy

  43. Size

  44. Atomic number, shielding, diagonal effect

  45. Reactivity

  46. Melting point?

  47. State!

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