A schematic shows a single piece of metal containing three distinct regions: • Region…
CHEMISTRY · Single correct · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
A schematic shows a single piece of metal containing three distinct regions:
• Region I – only aluminum atoms in a face-centered cubic array.
• Region II – some aluminum atoms are replaced by magnesium atoms of similar size.
• Region III – very small carbon atoms occupy many octahedral holes within the aluminum lattice.
Which statement correctly identifies the type of solid in each region and compares their electrical conductivities?
(a) Region I is a pure metal, Region II is a substitutional alloy, and Region III is an interstitial alloy; conductivity is greatest in Region III because the added carbon atoms introduce more charge carriers.
(b) Region I is a pure metal, Region II is a substitutional alloy, and Region III is an interstitial alloy; all three conduct electricity, but conductivity is expected to be greatest in Region I.
(c) Region I is a pure metal, Region II is an interstitial alloy, and Region III is a substitutional alloy; conductivity is greatest in Region II because the added magnesium atoms donate additional electrons to the sea of electrons.
(d) Region I is a pure metal, Region II is a substitutional alloy, and Region III is an ionic solid; conductivity would be greatest in Region III because mobile ions can carry charge through the lattice.