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Periodic Properties
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  1. Periodic Properties Chapter 7

  2. Periodic Properties Periodic Properties –depend on element’s position on table Ex: Groups H, Li, & Na all form similar oxides (H2O, Li2O, Na2O) Location gives you A LOT of information

  3. Periodic Properties 2 Main Factors for Periodic Properties • Number of Levels – More levels, electrons held less tightly • More shielding • More electron to electron repulsion (PUSH) • Number of Protons – More protons hold electrons more tightly. Greater effective nuclear charge (Zeff) (PULL)

  4. Periodic Properties Properties we will study: • Size of Atoms • Size of Ions • Ionization Energy • Multiple Ionization Energy • Electron Affinity

  5. Size of Atoms Atomic Radius 1. Measured in picometers (1pm = 1 X 10-12 m) or Angstroms (1 Å = 100 pm) 2. Average radius ~100 pm (1 Å)

  6. Size of Atoms 3. Example: Bromine 1.14 Å 1.14 Å X 100 pm = 114 pm 1 Å

  7. Effective Nuclear Charge Zeff = Z-S Z = # protons S = # core electron

  8. What is the Zeff for chlorine (1s22s22p63s23p5)? Zeff = Z-S Zeff = 17- 10 = 7+

  9. Size of Atoms Down a group • Atoms get larger (more levels) • Shielding Effect – Core electrons shield the pull of the nucleus (more electron repulsion) (PUSH wins) H 1 level Zeff = 1+ Li 2 levels Zeff= 1+ Na 3 levels Zeff = 1+

  10. Size of Atoms

  11. Size of Atoms Across a period – atoms get smaller (same level), greater Zeff(PULL wins) Li F E config Levels Zeff

  12. Size of Atoms Si Cl

  13. Size of Ions A. Positive Ions 1. Example: Mg Mg+ E config Levels Zeff

  14. Size of Ions

  15. Size of Ions Positive ions always smaller • Fewer electrons to control • Less e- to e- repulsion

  16. Mg Mg+ Mg2+ E config Levels Zeff

  17. Size of Ions B. Negative Ions 1. Example: O O2- O3- E config Levels Zeff

  18. Size of Ions

  19. Size of Ions Negative ions always larger • More electrons to control • More e- to e- repulsion

  20. More levels If same Greater Zeff (same levels, greater Zeff smaller) If same Ions Positive = smaller(less electron repulsion) Negative = Larger (more electron repulsion)

  21. Size Review Which is larger and why? Li or K S or S2+ Mg or S O or Te

  22. Size Review Kurveball K or K+

  23. Ionization Energy A.Ionization energy – The energy needed to remove an electron from an isolated gaseous atom or ion Na  Na+ + e-

  24. He Ne Ar H Li Na K

  25. A high energy photon may ionize an atom (completely remove the electron) PHOTOELECTRIC EFFECT A low energy photon will excite an electron BOHR MODEL

  26. Ionization Energy B. Ionization energy is inversely proportional to atomic radius Examples: Li (520 kJ/mol) F (1681) Na (496 kJ/mol) Cl (1251)

  27. Ionization Energy Which has the higher Ionization Energy and why? C or O Na or Cl C or Sn Mg or Ra

  28. Multiple Ionization Energy Multiple Ionizations - Removing more than one electron 1st Mg  Mg+ + e- 738 kJ/mol 2nd Mg+  Mg2+ + e- 1450 kJ/mol 3rd Mg2+  Mg3+ + e- 7732 kJ/mol There is a large jump once you reach Noble Gas Configuration (Fewer levels, spike in Zeff)

  29. Multiple Ionization Energy

  30. Multiple Ionization Energy 1st Al  Al + + e- 577 kJ/mol 2nd Al +  Al 2+ + e- 1816 kJ/mol 3rd Al2+  Al3+ + e- 2744 kJ/mol 4th Al3+  Al4+ + e- 11580 kJ/mol

  31. Multiple Ionization Energy Examples: a. Where will the large jump in I.E. occur for: Be B P b. Element X has a large jump between its 4th and 5th I.E. To what group does it belong?

  32. Electron Affinity • Energy change that occurs when an electron is added to an isolated gaseous atom or ion • Ease with which an atom gains an electron • Cl(g) + e-  Cl-(g) DE = -349 kJ/mol • Positive for noble gases (don’t want electrons)

  33. Properties of Metals • Malleable and ductile • Good conductors • Large radius/Low ionization energy • Form positive ions (+2 and +3 for transition metals)

  34. Metal Oxides • Most metals oxidize easily in the atmosphere 2Ni(s) + O2(g)  2NiO(s) • Metal oxides are bases Metal Oxide + Water  Metal hydroxide (base) Na2O(s) + H2O(l)  2NaOH(aq) CaO(s) + H2O(l)  Ca(OH)2(aq) Metal Oxide + Acid  Salt + Water MgO(s) + HCl(aq)  MgCl2(aq) + H2O(l) NiO(s) + H2SO4(aq)  NiSO4(aq) + H2O(l)

  35. Al(s) + O2(g)  Zn(s) + O2(g)  CaO(s) + H2O(l)  Li2O(s) + H2O(l)  Al2O3(s) + HNO3(aq)  CuO(s) + H2SO4(aq) 