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Lecture 8

Lecture 8. Ions and Ionic Compounds 2.1-2.6 8 -September Assigned HW C5, C6, 2.1, 2.3, 2.4 Due: Monday 13-Sept. Review C, D1-D3, 2.1. When 2 or more elements interact, they form compounds Organic – Carbon Containing – Covalent Bonds

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Lecture 8

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  1. Lecture 8 Ions and Ionic Compounds 2.1-2.6 8-September Assigned HW C5, C6, 2.1, 2.3, 2.4 Due: Monday 13-Sept

  2. Review C, D1-D3, 2.1 • When 2 or more elements interact, they form compounds • Organic – Carbon Containing – Covalent Bonds • Inorganic – Everything else – Covalent or ionic Bonds • Inorganic Compounds are composed of anions and cations • Looking for Noble Gas configuration  predictable trends in oxidation state from position in periodic table: • Group 1  +1 • Group 2  +2 • Group 16  -2 • Group 17  -1 • Transition metals need special consideration to predict oxidation states – typically multiple are possible. • +2 comes from losing electrons from s orbitals • Full and ½ full orbital set is desirable. • P-block can take on many oxidation states as well • Naming: • Memorize the list! • Electrostatic Neutrality • 4 rules: identify, name, name, combine • Sometimes water is present  hydrate

  3. Ions Make Up Rocks Different types of rocks break with distinct patterns Why might this be? What are they made up of?

  4. Ions Make up Rocks Example: Sodium chloride All rocks are inorganic compounds - some much more complicated than others – organized into lattices.

  5. Ions Make up Rocks

  6. Ions Make up Rocks Example: Sodium chloride What do we know about the energy that stabilize charged species?

  7. Favorable and Unfavorable Energies Not Favorable Why is the sign (+)? Why is the radius 2d? Favorable d d ? Why is the sign (-)? Why is the radius d?

  8. Adding Up the Energies Not Favorable Favorable d d

  9. Adding Up the Energies Energy stabilizing an ion on the edge of a crystal. What if it’s in the middle? Not Favorable Favorable d d

  10. Adding Up the Energies 2 directions d d Not Favorable Favorable

  11. Adding Up the Energies – 4 directions

  12. Adding Up the Energies – 6 directions y z Now imagine a third dimension x

  13. Adding Up the Energies – Multiple Layers 2D

  14. Adding Up the Energies – 3 Dimensions A is the Madelung Constant which depends on how the ions are arranged relative to one another. Which of these values are similar? Why? CsCl CaF2 NaCl MgF2

  15. Adding Up the Energies – Bone Example: Calcium Phospahte What is the chemical formula? +2 -3 Will this be stable as drawn? +2 +2 -3 +2 -3 -3 +2 +2

  16. Adding Up the Energies – Bone 3D Example: Calcium Phospahte

  17. Adding Up the Energies – 3 Dimensions Would you expect the stabilization energy to be greater for NaCl or MgO? What might influence the stabilization energy?

  18. Adding Up the Energies – Infinite Repulsion What would happen if the crystal got so small that these radii became important ?

  19. Using the Lattice Energy Additional term to account for significant repulsions between neighbors when they come into contact. We can predict the distance between ions using the potential energy equation. Identify the point on the graph that indicates the most likely distance between ions.

  20. Compounds Compound Bond Type Inorganic Compound Organic Compound Covalent Composed of Charged components Ionic Bonds Contains Carbon Cations Anions

  21. Lewis Representation – Ionic Bond • American chemist G.N. Lewis had a profound impact on our understanding of chemical bonding. One of his many contributions was a simple way to represent chemical bonds. We call these Lewis Symbols. • Valence Electrons are represented by dots. • A single dot represents an electron • A pair of dots represents two paired electrons sharing an orbital H He N O Cl K Mg I 1s1 1s2 2s22p3 2s22p4 2s22p5 3s1 5s25p5 3s2

  22. Lewis Representation – Ions and Ionic Bonds Ionic bonds do not share electrons – bond due to coulombic attraction Ion Electron Configuration Lewis Symbol H+ O2-Cl- K+ Mg2+ Example: NaCl CaCl2  H O Cl K Mg

  23. Lewis Representation – Covalent Bonds Covalent bonds  electrons shared between two atoms. This involves an overlap of atomic orbitals Let’s consider H2 - two hydrogen atoms share electrons. H• H H + H• Commonly represented as: H H Solid line represents covalent bond

  24. Lewis Representation – Covalent Bonds F2 Only the unpaired electron is involved in bonding. F• + F• How would this look if we were making Cl2?

  25. Lewis Representation – Covalent Bonds HF Start Finish The Octet Rule – non-metals share electrons until each has a complete octet (or duplet for H and He).

  26. Lewis Representation – Covalent Bonds CH4 Start Finish C H H H H

  27. Common Representations of Compounds

  28. Common Representations of Compounds Ethanol OH

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