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Chapter 6 Ionic Bonds and Some Main Group Chemistry

Chapter 6 Ionic Bonds and Some Main Group Chemistry. Ions and Their Electron Configurations. Chapter 2 Metals lose electrons to form cations Main group elements tend to lose the same # of electrons as their group number to attain nearest noble gas configuration Na, Ne, Na + O, Ne, O 2-

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Chapter 6 Ionic Bonds and Some Main Group Chemistry

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  1. Chapter 6 Ionic Bonds and Some Main Group Chemistry

  2. Ions and Their Electron Configurations • Chapter 2 • Metals lose electrons to form cations • Main group elements tend to lose the same # of electrons as their group number to attain nearest noble gas configuration • Na, Ne, Na+ O, Ne, O2- • K, Ar, K+ Cl, Ar, Cl- • Ga, Ga3+ Sn, Sn4+ • Nonmetals when combined with metals gain electrons to form anions • The number gained = 8 – group #

  3. Periodic Table and Electron Configurations • Build-up order given by position on periodic table; row by row. • Elements in same column will have the same outer shell electron configuration.

  4. Ions and Their Electron Configurations

  5. 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f Diagonal Rule for Build-up Rule • The periodic table can also be used to determine the electron configuration of an element.

  6. Ions and Their Electron Configurations Atoms Ions + 3 e- + 2 e- + 1 e- - 1 e- - 2 e- - 3 e- N: O: F: Na: Mg: Al: 1s2 2s2 2p3 1s2 2s2 2p4 1s2 2s2 2p5 1s2 2s2 2p6 3s1 1s2 2s2 2p6 3s2 1s2 2s2 2p6 3s2 3p1 N3-: O2-: F1-: Ne: Na1+: Mg2+: Al3+: 1s2 2s2 2p6 1s2 2s2 2p6 1s2 2s2 2p6 1s2 2s2 2p6 1s2 2s2 2p6 1s2 2s2 2p6 1s2 2s2 2p6

  7. Ions and Their Electron Configurations • Transition element ions formed by • 1st losing their valence electrons • 2nd losing d-orbital electrons to obtain the charge • Fe2+ Fe3+ Co2+ Co4+ • Ag+ Zn2+

  8. Anomalous Electron Configurations • A few exceptions to the Aufbau principles exist. Stable configuration: • half-filled d shell: • Cr has [Ar]4s13d5; • Mo has [Kr] 5s14d5 • filled d subshell: • Cu has [Ar]4s13d10 • Ag has [Kr]5s14d10. • Au has [Xe]6s14f145d10 • Exceptions occur with larger elements where orbital energies are similar.

  9. Ions and Their Electron Configurations Atoms Ions [Ar] 4s2 3d6 [Ar] 4s2 3d6 Fe2+: Fe3+: [Ar] 3d6 [Ar] 3d5 - 2 e- - 3 e- Fe: Fe:

  10. Ionic Radii • Effect of charge on ionic radii evaluated using atomic size and Zeff • Atomic size increases with increasing energy levels • Zeff • Cation – more protons than electrons – stronger attraction • Anion – less protons than electrons – weaker attraction • Cation < Neutral atom < anion

  11. Ionic Radii

  12. Ionic Radii

  13. Atomic Radius • Atomic radii actually decrease across a row in the periodic table. Due to an increase in the effective nuclear charge. • Within each group (vertical column), the atomic radius tends to increase with the period number.

  14. Ionization Energy Ionization Energy (Ei): The amount of energy necessary to remove the highest-energy electron from an isolated neutral atom in the gaseous state.

  15. Ionization Energy

  16. Ionization Energy Boron has a lower Ei due to a smaller Zeff (shielding by the 2s electrons)

  17. Ionization Energy Oxygen has a lower Ei since the first electron is removed from a filled orbital

  18. M + energy M1+ + e- M1+ + energy M2+ + e- M2+ + energy M3+ + e- Higher Ionization Energies

  19. Problem • Which of the following elements has the smallest first ionization energy?  • A.  Rb • B.  Mg • C.  I • D.  As • E.  F

  20. Problem • Which of the following elements has the largest second ionization energy (IE2)?  • A.  Li • B.  B • C.  O • D.  F • E.  Na

  21. Electron Affinity • Electron Affinity (Eea) - Describes the energy associated with the absorption of 1 mole of electrons by 1 mole of gaseous atoms • Cl + e- Cl- • Can be positive or negative • Positive – energy had to be added to force the atom to absorb the electron (non-favored) • Negative – energy was given off when the electron was added to the atom (favored)

  22. Electron Affinity Electron Affinity (Eea): The energy released when a neutral atom gains an electron to form an anion.

  23. Problem • Select the element with the most negative electron affinity (i.e., accepts an electron most readily).  • A.  H • B.  Li • C.  C • D.  F • E.  Ne

  24. Larger Larger Larger Larger Larger Larger Trends in Size, IE, and EA Size • IE, and EA are the opposite of atomic radius Ionization energy Electron Affinity

  25. Ionic Bonds and the Formation of Ionic Solids • Calculate the lattice energy (in kJ/mol) for the formation of CaH2 from its elements. • Calculate the overall energy change (in kJ/mol) for the formation of CaCl from its elements. • Calculate the overall energy change (in kJ/mol) for the formation of CaCl2 from its elements. • Which is more likely to form, CaCl or CaCl2?

  26. Ionic Bonds and the Formation of Ionic Solids • Trends in Lattice Energy • Increases with increasing charge • Increases with decreasing ion size

  27. Ionic Bonds and the Formation of Ionic Solids 1s2 2s2 2p6 3s1 1s2 2s2 2p6 3s2 3p5 Na + Cl Na1+ Cl1- 1s2 2s2 2p6 1s2 2s2 2p6 3s23p6

  28. Ionic Bonds and the Formation of Ionic Solids Born-Haber Cycle

  29. Na(s) + Cl2(g) Na1+(g) + Cl1-(g) Cl(g) + e- Cl2(g) Na(g) Na(s) NaCl(s) Cl(g) Cl1-(g) NaCl(s) Na1+(g) + e- Na(g) 1 1 2 2 Ionic Bonds and the Formation of Ionic Solids Born-Haber Cycle Step 1: +107.3 kJ/mol Step 2: +122 kJ/mol Step 3: +495.8 kJ/mol Step 4: -348.6 kJ/mol Step 5: -787 kJ/mol -411 kJ/mol

  30. Lattice Energies in Ionic Solids Lattice Energy (U): The amount of energy that must be supplied to break up an ionic solid into individual gaseous ions.

  31. The Octet Rule Octet Rule: Main-group elements tend to undergo reactions that leave them with eight outer-shell electrons.

  32. The Octet Rule Octet Rule: Main-group elements tend to undergo reactions that leave them with eight outer-shell electrons. Metals tend to have lowEi and lowEea. They tend to lose one or more electrons. Nonmetals tend to have highEi and highEea. They tend to gain one or more electrons.

  33. The Octet Rule • Electrons of metals are most likely lost due to the fact that: • core electrons are shielding them from the nucleus • Zeff is lower • Small ionization energies • Upon loss they obtain noble gas configuration

  34. The Octet Rule • Nonmetals are most likely to gain electrons due to the fact that: • no additional shielding occurs from the nucleus occurs due to core electrons • Zeff is higher • More negative electron affinities • Upon gain they obtain noble gas configuration

  35. The Octet Rule

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