Brass is a substitutional alloy that contains approximately 70 % copper and 30 % zinc by mass. A jeweler is interested in how alloying alters the bonding and physical properties relative to pure copper.
(a) Describe what happens at the atomic level when Zn atoms replace Cu atoms in the crystal lattice of brass. Include a discussion of electron delocalization.
(b) Pure copper is a better electrical conductor than brass. Use the metallic bonding model to account for the decrease in conductivity upon alloying with zinc.
(c) Brass is appreciably harder than pure copper. Explain this increase in hardness in terms of changes to metallic bonding and lattice structure produced by alloying.