Pure iron is malleable and conducts electricity well
CHEMISTRY · Single correct · GCSE · Chemistry · Bonding, Structure and the Properties of Matter · Bonding, Structure and the Properties of Matter
Problem
Pure iron is malleable and conducts electricity well. An interstitial alloy of iron containing a small percentage of carbon (steel) conducts electricity about as well as pure iron but is significantly harder and less ductile. Which statement best explains these observations?
(a) Carbon atoms substitute for some iron atoms in the lattice, distorting the structure; the distortion makes the metal harder but also scatters electrons, so conductivity should decrease.
(b) Adding carbon contributes extra valence electrons to the electron sea, enhancing both hardness and electrical conductivity.
(c) Carbon atoms occupy interstitial spaces in the iron lattice, restricting the movement of metal atom layers and increasing hardness, while the sea of delocalized electrons remains largely unaffected, so electrical conductivity stays high.
(d) Carbon forms ionic bonds with iron atoms, producing a rigid but brittle lattice that greatly lowers electrical conductivity.