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Ionic Bonds and Main Group Chemistry

Ionic Bonds and Main Group Chemistry. Chapter 6. Ionization Energy. The amount of energy required to remove the outermost electron form an isolated neutral atom in the gaseous state. Higher ionization energies. Ionization energy always increases as you pull off more electrons.

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Ionic Bonds and Main Group Chemistry

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  1. Ionic Bonds and Main Group Chemistry Chapter 6

  2. Ionization Energy • The amount of energy required to remove the outermost electron form an isolated neutral atom in the gaseous state.

  3. Higher ionization energies • Ionization energy always increases as you pull off more electrons. • Ionization energies take a huge leap when we try to remove an electron from a new inner shell.

  4. Electron Affinity • The energy change that occurs when an electron is added to an atom (or ion) in the gaseous state. Frequently costs nothing but actually yields energy therefore EA’s are usually negative.

  5. Ionic Bonds • Ions are held together by ionic attraction where the force of attraction is governed by Coulomb’s Law. • Makes sense • Large Z  strong attraction  larger E • Large d  charge felt less  smaller E Z=ion charge d = distance between nuclei

  6. Lattice Energies

  7. Formation of ionic compounds • Get elements as atoms (generally requires energy) • Form ions (anions are energetically favorable, cations are unfavorable) • Bring ions together (favorable) • Condense to solid phase (favorable)

  8. Energetics of NaCl Formation • Na(s) Na(g) +107.3 kJ/mol • Na(g)  Na+ + 1e +495.8 kJ/mol • 1/2 Cl2(g)  Cl (g) +122 kJ/mol • Cl(g)  Cl(g) 348.6 kJ/mol • Na+(g) + Cl(g)  NaCl(s) 787 kJ/mol • ==================================== • Na(s) + 1/2 Cl2(g)  NaCl(s) 411 kJ/mol

  9. Determine the energy of formation of MgCl2 from the elements.

  10. magnesium bromide • Mg(s)  Mg(g) +147.7 kJ/mol • Mg(g)  Mg+ + 1e +737.7 kJ/mol • Mg+(g)  Mg2+(g) + 1e +1450.7 kJ/mol • Br2(g)  2 Br (g) +193 kJ/mol • 2Br(g)  2Br(g) 2(325 kJ/mol) • = 650 kJ/mol • Mg2+(g) + 2Br(g)  MgBr2(s) 2440 kJ/mol • ==================================== • Mg(s) + Br2(g)  MgBr2(s)  561 kJ/mol

  11. Calculate the energy released in kJ/mol in the reaction • Na(s) + 1/2 I2(s)  NaI(s) • The energy of vaporization of Na(s) is 107 kJ/mol. The sum of the • enthalpies of dissociation and vaporization of I2(s) is 214 kJ/mol, and the lattice energy of NaI is 704 kJ/mol.

  12. Calculate the energy released in kJ/mol when LiH is formed in the reaction • Li(s) + ½ H2(g)  LiH(s) • Heat of vaporization, Li 161 kJ/mol • Dissociation energy, H2 436 kJ/mol • Lattice energy, LiH -917 kJ/mol • Ionization energy, Li 520 kJ/mol • Electron affinity, H -73 kJ/mol • Answer: -91 kJ/mole net change

  13. Descriptive Chemistry • Alkali Metals • Alkaline Earths • Aluminum • Halogens • Nobel Gases

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