Structures of Solids

Question 1

What are the 4 classes of solids?

Answer 1

metallic, ionic, covalent network, molecular

Question 2

metallic solids

Answer 2

held together by a “sea” of shared electrons(nuclei like islands), this allows metals to conduct electricity and be strong and NOT brittle
Ex: Cu, Fe

Question 3

ionic solids

Answer 3

Held together by strong attraction between cations and anions. They generally do NOT conduct electricity
Ex: NaCl, MgO

Question 4

Covalent Network solids

Answer 4

Held together by covalent bonds. Typically a bunch of non-metals. This bonding type makes materials very hard (like diamonds). Semiconductors
Ex: diamond, graphite

Question 5

Molecular solids

Answer 5

Held together by the intermolecular forces (hydrogen-bonding, dipole-dipole, dispersion). This is the weakest solid. Soft, low melting points.
Ex: HBr, H2O

Question 6

What is a unit cell?

Answer 6

a small repeating unit stacked over and over, 3-dimensionally, in all directions to make a solid

Question 7

3 types of unit cells for solids?

Answer 7

1) simple cubic
2) body-centered cubic
3) face-centered cubic

Question 8

How many atoms in a simple cubic unit cells?

Answer 8

1 atom per unit cell. Atoms at corners of cube (so 8 atoms each, bot only 1/8 of each atom is inside the box. So only ONE full atom for unit)

Question 9

How many atoms in a body-centered cubic unit cell?

Answer 9

2 atoms per unit cell. #1 fully inside the box and eight straddling each corner making #2 (1/8*8=1)

Question 10

How many atoms in a face-centered cubic unit cell?

Answer 10

4 atoms per unit cell. atoms at corners and on flat surface sides. half of each atom on the sides is inside the box. (corners= 1/88=1, sides =1/26=3)