Iron is extracted from iron oxide by displacement with carbon.But aluminum is not extracted from aluminium oxide using displacement by carbon. Suggest a reason for this.
Well, de facto because the heat of formation of aluminum oxide is so much greater than the heat of formation of iron oxide. If you're looking for something more mechanistic, find Al and Fe in the periodic table. Al and Fe are in different rows, and Fe is larger than Al, so although Al+3 and Fe+3 have the same charge, oxygen bonds less strongly to Fe+3 than to Al+3 because it's further away from the nucleus of Fe. Al+3 has no outer shell electrons at all; 3s, 3p, and 3d subshells are all empty. It's effectively a charged sphere with nothing to interfere with bonding. Fe+3 (as in hematite, Fe2O3) is larger, has filled 3s and 3p subshells, and a half-filled 3d subshell. That 3d electron density projects pretty far out into space, holding oxygen at arms length. Aluminum has no electron density in 3d orbitals, so oxygen can tuck in nice and tight and get a good grip. Any of these hit the mark? I don't know what background you're bringing to this question.
