Unit Cells

Corner atom

1/8 atom

Face atom

1/2 atom

Body atom

1 atom

Simple Cubic (SC)

1 atom

Face-Centered Cubic (FCC)

4 atoms

Body-Centered Cubic (BCC)

2 atoms

1 pm

10⁻¹⁰ cm

Which type of unit cell has the highest packing efficiency?

Face-centered cubic (FCC)

A metal crystallizes in a body-centered cubic structure with an atomic radius of 125 pm. What is the edge length of its unit cell in pm?

Approximately 288 pm (using the formula a = 4r/√3)

What is the coordination number of an atom in a face-centered cubic (FCC) unit cell?

12

Which of the following statements about crystalline solids is true? (A) Amorphous solids have a well-defined repeating structure. (B) Body-centered cubic structures have a lower packing efficiency than face-centered cubic structures. (C) The density of a solid is independent of its crystal structure. (D) In a simple cubic unit cell

atoms are located only at the edges.

What fraction of an atom is shared at the corner of a simple cubic unit cell?

1/8