1. An Introduction to Structures and Types of Solids

2. Types of Solids The broadest categories of solids are:
- Crystalline solids-those with a highly
regular arrangement of their
components.
-Amorphous solids-those with
considerable disorder in their
structures

3. Components of Crystalline Solids
Lattice-a three-dimensional system of points designating the positions of the atoms, ions, or molecules
Unit cell-the smallest repeating unit of the lattice
See page 459 for the common unit cells and their lattices

4. Bragg Equation
Used to determine the spacing between layers of atoms in a crystal.
nλ = 2d sin θ
n is an integer, d is the distance between atoms, θ is the angle of incidence and reflection.

5. Example Problem Using the Bragg Equation
Example problem: X-rays of wavelength 1.54 angstrom were used to analyze an aluminum crystal. A reflection was produced at θ = 19.3o. Assuming n=1, calculate the distance between the planes of atoms producing this reflection.
Answer: 233 pm

6. Types of Crystalline Solids
Ionic Solids-ions are at the points of the lattice. Ex: Sodium chloride, NaCl
Molecular Solids-covalently bonded molecules at the points of the lattice
Ex: Ice, H2O molecules are at each point
Atomic Solids-atoms are at the points of the lattice. Ex: graphite (carbon at the lattice points)

7. Types of Atomic Solids
Metallic Solids- a special type of delocalized nondirectional covalent bonding occurs (this results in metals acting as good conductors of electricity)
Network Solids- nonmetallic atoms bond to each other with strong directional covalent bonds that lead to giant molecules, or networks, of atoms (example: carbon and silicon)

8. Types of Atomic Solids (continued)
Group 8A Solids-the noble gases are attracted to each other with London dispersion forces.
For a summary, see the Table 10.3 on page 463.

9. Gold is an example of a(n)10
Atomic solid with metallic properties
Network covalent solid
Molecular solid
Ionic solid 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

10. Carbon dioxide is an example of a(n)10
Atomic solid
Network covalent solid
Molecular solid
Ionic solid 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

11. Lithium fluoride is an example of a(n)10
Atomic solid
Network covalent solid
Molecular solid
Ionic solid 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

12. Krypton is an example of a(n)10
Atomic solid
Network covalent solid
Molecular solid
Ionic solid 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

13. Structure and Bonding in Metals
Metals are characterized by high thermal and electrical conductivity, malleability, and ductility.
These properties are traced to the nondirectional covalent bonding found in metallic crystals

14. Types of Metallic Crystals
Hexagonal Closest Packing-the spherical metal atoms are packed in layers in which each sphere is surrounded by 6 others.
In the second layer, the spheres do not lie directly over those in the first layer.
Instead, each occupies an indentation formed by three spheres in the first layer.
This arrangement is commonly referred to as an ABA arrangement.
Examples of metals that form hexagonal closest packing are Mg and Zn.

15. Types of Metallic Crystals (continued)
Cubic Closest Packing- the first two layers are the same as the hexagonal closest packing.
In the fourth layer, the spheres occupy the same vertical position (instead of the third)
This arrangement is commonly referred to as the ABC arrangement.
In the ABC arrangement, the unit cell is face centered.
Examples of metals that form cubic closest packing are Al, Fe, Cu, Co, and Ni.

16. Determining the Density of a Closest Packed Solid
Complete the practice problems on page 465

17. Determining the Number of Ions in a Unit Cell
See page 482