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Chapter 8 Periodic Properties of the Elements PART 2

Chapter 8 Periodic Properties of the Elements PART 2. Trends in Atomic Radius Transition Metals. Atoms in same group increase in size _____________ the column Atomic radii of transition metals roughly same size _____________________

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Chapter 8 Periodic Properties of the Elements PART 2

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  1. Chapter 8Periodic Properties of the Elements PART 2

  2. Trends in Atomic Radius Transition Metals • Atoms in same group increase in size _____________the column • Atomic radii of transition metals roughly same size _____________________ • much less diff than main group elements • valence shell ns2, not Tro: Chemistry: A Molecular Approach, 2/e 2

  3. Electron Configurations of Main Group Cations in Their Ground State • Cations form when atom loses e-’s from valence shell Al atom = Al3+ ion = Tro: Chemistry: A Molecular Approach, 2/e 3

  4. e- Configurations of Transition Metal Cations in their ground state 1st e-’s removed are valence e-’s e-’s may also be removed from Tro: Chemistry: A Molecular Approach, 2/e 4

  5. Transition Metal Cations • Fe atom has 2 valence electrons Fe atom = 1s22s22p6 • When cation forms, it first loses its valence e-’s Fe2+cation = 1s22s22p63s2 • It can then lose 3d electrons Fe3+cation = 1s22s22p6 Tro: Chemistry: A Molecular Approach, 2/e 5

  6. Magnetic Properties of Transition Metal Atoms & Ions • unpaired e-’s mean that atom or ion will have a net magnetic field = • Attracted to a mag field • e- configurations w/ all paired e-’s: atom or ion has nomagnetic field = Tro: Chemistry: A Molecular Approach, 2/e 6

  7. Transition Metal Atoms and Ions:Electron Configuration & Magnetic Properties • Both Zn atoms and Zn2+ ions are diamagnetic • shows two 4s electronsare lost Zn atoms: Zn2+ions: Tro: Chemistry: A Molecular Approach, 2/e 7

  8. Transition Metal Atoms and Ions:Electron Configuration & Magnetic Properties • Ag forms both Ag+ ions and, rarely, Ag2+ • Ag atoms [Kr]5s14d10 are • Ag+ ions [Kr]4d10 are • Ag2+ ions [Kr]4d9 are Tro: Chemistry: A Molecular Approach, 2/e 8

  9. Trends in Ionic Radius • Ions in same group have same charge • Ion size increases down the column • Cations < neutral atoms; anions > neutral atoms • Cations < anions • except Rb+ & Cs+ Tro: Chemistry: A Molecular Approach, 2/e 9

  10. Trends in Ionic Radius • Larger positive charge = smaller cation • for isoelectronic species • isoelectronic = • Larger negative charge = larger anion • for isoelectronic species Tro: Chemistry: A Molecular Approach, 2/e 10

  11. Periodic Pattern – Ionic Radius (Å) Tro: Chemistry: A Molecular Approach, 2/e 11

  12. Tro: Chemistry: A Molecular Approach, 2/e 12

  13. Practice – Order the following sets by size (smallest to largest) Zr4+, Ti4+, Hf4+ Na+, Mg2+, F−, Ne I−, Br−, Ga3+, In+ Tro: Chemistry: A Molecular Approach, 2/e 13

  14. Ionization Energy (IE) • Minimum Eneeded to remove an e-from an atom or ion Tro: Chemistry: A Molecular Approach, 2/e 14

  15. Ionization Energy (IE) • valence e- easiest to remove, lowest IE • M(g) + IE1 M1+(g) + 1 e- • M+1(g) + IE2  M2+(g) + 1 e- Tro: Chemistry: A Molecular Approach, 2/e 15

  16. Energetics of Ion Formation Ionization Energies: Energy is required to

  17. Ionization energy () is amount of energy needed to remove an e- from gaseous atom (call it “E”) in ground state: E (g) +  E+(g) + e- energy required for reaction =  IE is

  18. General Trends in 1stIE • The larger the Zeffon the e-, the moreEit takes to remove it • The farther the dist e- is from nucleus, the lessEit takes to remove it • 1st IE ______________down the group • 1st IE generally _____________across period Tro: Chemistry: A Molecular Approach, 2/e 18

  19. Tro: Chemistry: A Molecular Approach, 2/e 19

  20. 20 Tro: Chemistry: A Molecular Approach, 2/e 20

  21. Practice – Choose atom with largest first IE in each pair • Mg or P • Ag or Cu • Ca or Rb • P or Se Tro: Chemistry: A Molecular Approach, 2/e 21

  22. Exceptions in 1stIE Trends    N Be         1s 1s 1s 1s 2s 2s 2s 2s 2p 2p 2p 2p     B O • 1st IE generally increases from left to right across a Period • Except from 2A to 3A, 5A to 6A Tro: Chemistry: A Molecular Approach, 2/e 22

  23. Trends in Successive IE’s • Removal of each successive e- costs more energy • shrinkage  • outer e-’scloser to nucleus, • Regular increase in E for each successive valence e- • Large increase in E when start removing core e-’s Tro: Chemistry: A Molecular Approach, 2/e 23

  24. Trends in Successive IE’s Tro: Chemistry: A Molecular Approach, 2/e 24

  25. Ionization Energies: • It takes more energy to remove 2nd e- from an atom than 1st, and so on. • Two reasons for this trend: • 2nd e- is being removed from (+) charged species • not a neutral one,

  26. Ionization Energies: 2. Removing 1st e-reduces_____________________ among remaining e-‘s, so attraction of remaining e-’s to nucleus is stronger. Energy required to remove e-‘s from a filled core is prohibitively large

  27. Ionization Energies: Ionization energies of s- & p-block elements Elements in 3rd row, successiveionization energies increase steadily as e-’s are removed from valence orbitals (3s or 3p). Followed by a large increase in ionization energy when e-’s are removed from filled core levels.

  28. Some chemrxns release enough E to ionize atoms – but pulling e- off filled energy level? Tro: Chemistry: A Molecular Approach, 2/e 28

  29. Ionization Energies: Larger values of  mean that e- is more tightly bound to atom and is harder to remove. Ionization energy units: kilojoules/mole (kJ/mol) or electron volts (eV) 1 eV =

  30. Clicker Qstn: Which of the following element would be most likely to lose 3 e-’s: Gallium, Calcium, or Rubidium? Gallium Gallium & Calcium Gallium, Calcium, & Rubidium Calcium & Rubidium

  31. Clicker Qstn: Which of these elements would you predict to have the highestfirst ionization energy? Sn Sb As Ge

  32. On the basis of position in the periodic table, which of the following elements would you expect to have the lowestsecond ionization energy? Sr Rb Ar Si Clicker Question

  33. Electron Affinity (EA) • E released when neutral atom gains an e- • gas state • M(g) + 1e− M1−(g) + EA • Defined as exothermic (−), but may actually be endothermic (+) • some alkali earth metals & all noble gases are endothermic, WHY? • more E released, larger the EA • more negthe #, the larger the EA Tro: Chemistry: A Molecular Approach, 2/e 35

  34. Electron Affinity: Electron affinity (EA) of an element E defined as energy Dthat occurs when an e- is added to agaseousatom: E (g) + e-  E—(g) energy change = EA.

  35. Electron Affinity (EA): Electron affinities can be negative (energy released when e- added) positive (energy added to system –makes an anion) or zero (process is energetically neutral).

  36. Tro: Chemistry: A Molecular Approach, 2/e 39

  37. Properties of Metals & Nonmetals • Metals • malleable & ductile • shiny, lustrous, reflect light • conduct heat &electricity • most oxides____________ & __________ • form cations in solution • lose electrons in reactions  Tro: Chemistry: A Molecular Approach, 2/e 40

  38. Properties of Metals & Nonmetals • Nonmetals • brittle in solid state • dull, non-reflective solid surface • electrical and thermal insulators • most oxides are ________ and _____________ • form anions and polyatomic anions • gain electrons in reactions  Tro: Chemistry: A Molecular Approach, 2/e 41

  39. Nonmetals Elements w/ highelectronegativity and verynegativeelectron affinities and largeionization potentials Are electrical insulators – tend to gain electrons (reduced) in chemical reactions (they are oxidants)

  40. Metals Elements with lowelectronegativity and either positive or small negativeEA’s and smallionization potentials Good electrical conductors – tend to lose e-’s (oxidized) in chem rxns (are reductants)

  41. Electronegativity (C) differences between • metals and non-metals • > or = _______have high resistivity • = insulators • < or = _______ have low resistivity • = conductors

  42. Rules for assigning oxidation states based on relative electronegativities of elements: More electronegative element in binary compound is assigned a negative oxidation state

  43. Metallic character: how closely an element’s properties match ideal properties of a metal • More malleable and ductile, better conductors, and easier to ionize • ________________left-to-rightacross a period • metals at left of the period / nonmetals at right • ________________downthe column • nonmetals found at top of middle Main Group elements / metals found at the bottom Tro: Chemistry: A Molecular Approach, 2/e 47

  44. Tro: Chemistry: A Molecular Approach, 2/e 48

  45. Tro: Chemistry: A Molecular Approach, 2/e 49

  46. Choose the more metallic element in each pair • Mg or Al • Si or Sn • Br or Te • Se or I Tro: Chemistry: A Molecular Approach, 2/e 50

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