A metallurgical engineer prepares an alloy by melting together elemental samples of…
CHEMISTRY · Multi-part · GCSE · Chemistry · Bonding, Structure and the Properties of Matter · Bonding, Structure and the Properties of Matter
Problem
A metallurgical engineer prepares an alloy by melting together elemental samples of Metal A and Metal B. The atomic (metallic) radii of the two elements, measured in picometres (pm), are shown below.
Metal Atomic radius / pm
A 135
B 138
Assume the solidified alloy retains the face–centred cubic (fcc) lattice of Metal A.
Answer the following questions about the structure of the alloy in the context of metallic bonding.
(a) Using only the data provided, classify the predominant type of alloy (substitutional or interstitial) that will form between Metals A and B. State clearly which element occupies which lattice positions.
(b) Justify your classification in part (a) by discussing the relative atomic sizes in the context of lattice packing efficiency and the metallic bonding model (positive ion cores in a sea of delocalised electrons). Your answer should explicitly address how the size comparison affects the ability of atoms to substitute for one another.
(c) Describe qualitatively how the predicted alloy structure in part (a) would influence two bulk properties—malleability and electrical conductivity—compared with those of pure Metal A. Support each prediction with reasoning based on atomic-level structure.