CHEMISTRY · Single correct · GCSE · Chemistry · Bonding, Structure and the Properties of Matter · Bonding, Structure and the Properties of Matter
Problem
Metal X has an atomic radius of 100 pm, whereas element Y has a radius of 85 pm. Some references state that substitutional alloys generally form when the atomic radii of the components differ by no more than roughly 15 %. Which explanation best justifies classifying an X–Y solid solution as substitutional rather than interstitial?
(a) Because the atomic masses of X and Y are nearly identical, the atoms can be exchanged in the lattice without causing strain, making the alloy substitutional.
(b) The 15 % size difference produces only limited lattice distortion, allowing Y atoms to replace X atoms at lattice sites.
(c) Because Y is much smaller than X, it can readily occupy the octahedral holes between X atoms without altering the crystal structure.
(d) The substantial difference in electronegativity between X and Y favors substitution over interstitial incorporation.