Chapters 25-30 Flashcards
What is a crystal lattice?
A repeating geometric arrangement of atoms or molecules in space.
What is a unit cell?
The simplest repeating arrangement of atoms that can describe a crystal lattice unambiguously.
Approximately how much of the periodic table is metals?
3/4s
In 2-dimensional unit cells, what variables are of necessary?
2 sides, a and b. And the angle between them, alpha.
What are the a, b and alpha values in a square 2-D unit cell?
a = b, alpha = 90 degs.
What are the a, b and alpha values in a hexagonal 2-D unit cell?
a = b, alpha = 120 degs.
What are the a, b and alpha values in a rectangular 2-D unit cell?
a not = b, alpha = 90 degs.
What are the a, b and alpha value in an oblique 2-D unit cell?
a not = b, alpha not = to 90 or to 120 degs.
What are the a, b and alpha values in a centered rectangular 2-D unit cell?
a not = b, alpha = 120 degs.
How many 3-D unit cells are possible? What are they called?
- Bravais lattices.
When were Bravais lattices identified?
1848.
How many of the 14 Bravais lattices are cubic?
- primitive, body-centered, and face centered.
How efficiently is the space filled in a primitive cubic unit cell?
52%
What is the only metal with a primitive cubic lattice strucuture?
Polonium
How many nearest neighbors do the atoms in a primitive cubic lattice have?
6.
How efficiently is the space filled in a body-centered cubic lattice?
68%
How many nearest neighbors do the atoms in a body-centered cubic lattice have?
8
How efficiently is the space filled in a face-centered cubic lattice?
74%.
What two types of alloys are t here?
solid solutions and intermetallic compounds.
What is a solid solution?
2 molten metals are mixed in just about any composition. The metal atoms may bethoroughly mixed overall, but their arrangement within the product are not highly ordered.
What is an intermetallic compound?
a very specific ratio of metal atoms is combined into a new, highly ordered, and sometimes very complex lattice.
What are ionic solids?
Solids such as NaCl which form regular lattices in which atoms give up and receive electrons.
What are molecular solids?
Ones in which the atoms of individual molecules are strongly bonded covalentlly, but the molecules are held to each other by weaker inter molecular forces.
What is a network covalent material?
One in which covalent bonding chains reach across huge networks of atoms, bonding the entire solid together with great strength.
