Three students draw 2-D particle-level diagrams to represent a sample of brass (an alloy containing copper and zinc). In each diagram, circles represent metal atoms of equal size unless otherwise noted.
• Diagram 1: All circles identical and arranged in a hexagonal close-packed pattern.
• Diagram 2: A hexagonal close-packed pattern in which one out of every six circles is replaced by a slightly lighter-shaded circle of the same size.
• Diagram 3: A hexagonal close-packed pattern in which small dark dots are drawn in some of the triangular holes between the larger circles.
Which diagram best represents brass?
a) Diagram 3
b) Diagram 2
c) Diagrams 2 and 3
d) Diagram 1