CHM 2353 Lecture Notes - Lecture 13: Diborane, Colemanite, Red Mud
7 Nov 2017
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Document Summary
No trend in melting point due to structural differences. Boron is an icosahedral structure, aluminum is a face centred cubic structure. Melting point depends on the stability of the structure. Once melted, more stable structure have no advantage because there are no more structures. The boiling point is then controlled by elemental properties. As nuclei become heavier, the +1 oxidation state becomes more favourable. Ga and in: +3 favoured, +1 can occur. Inert pair effect: tendency for heavier metals in groups beyond group 4 to lose only the p electrons. The remaining 2 s electrons are the inert pair of electrons. S orbitals penetrate closer to the nucleus than p orbitals, so s electrons are held more tightly than p electrons. As the principle quantum number increases, this effect increases > increases down a group. When elements have a +3 oxidation state, their cd is high and they have the tendency to form covalent bonds.
