When small carbon atoms occupy interstitial sites in an iron lattice to form steel
CHEMISTRY · Single correct · A Level · Chemistry · Bonding · Bonding
Problem
When small carbon atoms occupy interstitial sites in an iron lattice to form steel, the measured electrical conductivity at 25∘C remains nearly the same as that of pure iron. Which statement best explains this observation?
(a) Carbon atoms introduce extra free electrons via charge transfer, so any scattering caused by lattice distortion is exactly offset and conductivity remains unchanged.
(b) Interstitial carbon decreases lattice vibrations that scatter electrons, thereby maintaining the conductivity of the alloy.
(c) The delocalized electrons in the iron lattice stay mobile, and the slight lattice distortion produced by interstitial carbon is not enough to impede their motion.
(d) Because carbon is more electronegative, it draws electrons away from iron atoms; the reduced electron density is compensated by shorter paths between atoms, resulting in no net change in conductivity.