Bonding and Structure in Solids

1. Bonding and Structure in Solids SCH4U

2. Structure in solids Crystalline Solids: the atoms, ions, or molecules are ordered in well-defined three-dimensional arrangements. Have faces and make definite angles. Amorphous solids: a solid in which particles have no orderly structure. There is no well-defined shape or face. Solids do not stack well together. Eg. Rubber or Glass

3. Crystalline vs. Amorphous Structures

4. Types of Solids • Solids are held tightly by significant intermolecular forces. We can classify solids based on the type of intermolecular force holding the together • 1.Molecular Solids • 2. Covalent Solids • 3. Ionic Solids • 4. Metallic Solids

5. **Structures of Crystalline Solids (AP) ** Unit Cell  Crystal Lattice  Each repeating unit is reffered to as a Unit Cell. Unit cells create a crystal lattice.

6. Types of Unit Cells • Each has a different arrangement of lattice points. • There are seven basic types of unit cells. • Cubic Unit Cell • Primitive Cubic • Body Centered Cubic • Face-Centered Cubic

7. Types of Unit Cells

8. Sample Problem Determine the net number of Na+ and Cl- ions in the NaCl unit cell shown in the Figure.

9. Sample Problem Determine the net number of Na+ and Cl- ions in the NaCl unit cell shown in the Figure.

10. Close Packing of Spheres Arrangement of particles in closest contact to maximize attractive forces. Hexagonal Close Packing ABAB pattern Cubic Close Packing  ABCA Pattern

11. ** AP** Structure and Bonding in Metals* Extra Resources • https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Physical_Properties_of_Matter/States_of_Matter/Properties_of_Solids/Crystal_Lattice/Closest_Pack_Structures • http://faculty.sites.uci.edu/chem1l/files/2013/11/RDGcrystallinesolids.pdf • http://apchemistrynmsi.wikispaces.com/file/view/10+IMFs%2CSolids+%26+Liquids.pdf • Read pages 8-9

12. 1. Molecular Solids • Substances who’s particles are molecules. • Molecules are not strongly attracted together. • Intermolecular Forces include: London Dispersion Forces. • Some may include dipole-dipole forces and hydrogen bonding • Characterized by: • Low Melting and Boiling Points • Non-conductors

13. 1. Molecular Solids H-bonds become rigid, forming a lattice like structure • Examples include • Iodine, I2 (solid at room temperature) • Neon, Ne(m.p.=-248°C) • Solid CO2 ( mp -78.15°C ) • Ice (H2O) • Sugar

14. 2. Metallic Solids https://www.youtube.com/watch?v=aolRO9eteSk • Metals have very strong intermolecular forces binding their atoms together  not fully understood. • Metals, are substances that typically have a very high melting point. Most have b.p of above 1000°C • Except Mercury  melts at -39°C • Gallium  melts at 30°C

15. 2. Metallic Solids The outer electrons are so weakly bound to metal atoms that they are free to roam across the entire metal. Having ‘lost’ their outer electrons, individual metal atoms are more like positive ions in a swarm of communal electrons. Valence electrons are typically in s or d sub-shell. Electrons of neighboring atoms combine to form ‘electron soup’ that acts as a ‘glue’ to hold the positive nuclei of metal atoms together. These are called delocalized electrons.

16. 3. Metallic Solids Electron Sea Theory is a theory that states that the electrons in a metallic crystal move freely around the positively charged nuclei

17. Rice Krispy Analogy! Rice Krispy squares are an excellent analogy for metal solids. The marshmellow represents the delocalized electrons, and the rice are the positive metal ions.

18. Other Properties

19. 3. Ionic Solids • Substances who’s particles are ions --. Have completely given away or gained an electron. • An ionic compound is considered to be held by intramolecular forces. • Forms ions  opposite ions attract  ionic Bond

20. 3. Ionic Solids • Some properties of metals include: • They have very high melting points • They are brittle; they do not bend and putting too much stress causes them to break • Soluble in Water • In a solid state, do not conduct electricity • In a liquid, or molten state, they are electrically conductive.

21. 3. Ionic Solids

22. 4. Covalent Network Solids • Consists of atoms held together by large networks or changes by covalent bonds. • Every atom is bonded forming a 3-D network • C & Si  tend to form covalent network solids. • Eg: Diamond, Graphite, Silica and Asbestos. • Very high melting points • Extremely hard substances • Poor conductors of electricity

23. Diamond Allotrope of carbon Every carbon is bonded with 4 other carbons Extremely high crystal lattice energy resulting in characteristic hardness and high melting point.

24. Graphite • Allotrope of carbon • Each carbon forms a trigonal planar geometry • Crystal structure forms ‘sheets’ of covalently bonded carbons. • Sheets are not bonded together and as a result, slide over one another easily ( pencils! ) • Unique fact: • Carbon is a nonmetal, but graphite conducts electricity!

25. Diamond vs Graphite

26. Quartz Crystal

27. Bonding in Crystalline Solids

28. Homework Reminder: Test on Monday, October 30, 2017 • SCH4U • In-Class Worksheet • Types of Solids Assignment • Design lab procedure for next class • Read 4.3 (p.196-207) q’s p. 208 # 1-10 • Chapter 4 Review  pg. 209 # 1-31 • SCH4U- AP • In-Class Worksheet • Types of Solids Assignment • Design lab procedure for next class • Read 11.7 & 11. 8 • Q’s pg. # 471 69-78

29. Test Topics SCH4U : Chapter : 4.1, 4.2, 4.3 SCH4U- AP - 8.1-8.7, 9.1 -9.3, 11.1-11.2, 11.7-11.8 Ionic, Covalent and Metallic Bonding Lewis Structures VSEPR Shapes Polarity & Properties Intermolecular Forces Types of Solids