Lecture 6 - Crystal Structure 2

Question 1

What is a unit cell

Answer 1

Small repetitive volume which contains the complete lattice pattern of a crystal

Question 2

Difference between simple vs centred cubes

Answer 2

Simple only have atoms at the corner of cubes or rhomboids
Centered have additional atoms -
Body centred extra atom in the middle of the cube
Face centred extra atom in the middle of each face of the cube

Question 3

Which material has the highest density

Diamond
Plastic
Gold
Wood

Answer 3

Gold

Question 4

Why does metals have the highest density

Answer 4

Metals have close packing (metallic bonding)
Often large atomic masses
P of metals > p ceramics > p polymers

Question 5

Why are ceramics less dense than metals

Answer 5

Ceramics have loess dense packing
Often lighter elements

Question 6

Why is polymers the least dense from ceramics and metals

Answer 6

Polymers have low packing density (often amorphous)
Lighter elements (C,H,O)