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CHEM 114 Fundamental Chemistry

Germanium and semiconductors. Semiconductor. Metal. Fermi level. Conduction band. Conduction band. Valence band. α-germanium has the same structure as diamond/elemental silicon. Valence band. α-germanium was the first semiconductor discovered. Band gap (0.7 V).

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CHEM 114 Fundamental Chemistry

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  1. Germanium and semiconductors Semiconductor Metal Fermi level Conduction band Conduction band Valence band α-germanium has the same structure as diamond/elemental silicon. Valence band α-germanium was the first semiconductor discovered. Band gap (0.7 V) Usually tetravalent (GeCl4, GeO2) but occasionally divalent (GeO) CHEM 114 Fundamental Chemistry GeF4 is a gas; GeCl4 is a liquid that reacts with water. GeO2 is an amphoteric oxide, but mostly acidic: GeO2 + 2 OH– → H2GeO42– GeO2 + 4 HCl → GeCl4 + 2H2O

  2. The group 14 metals CHEM 114 Fundamental Chemistry Sn(II), Pb(II) compounds are ionic. Sn(IV), Pb(IV) compounds are more covalent. Sn and Pb have amphoteric oxides (form tin, lead salts in acid; stannate/plumbates in alkali.

  3. The group 15 elements CHEM 114 Fundamental Chemistry

  4. NOx Linear, 1 and 2 coordinate N: Diatomic, 1 coordinate N: Planar, 3 coordinate N: Planar, 3 coordinate N: Planar, 3 coordinate N: Planar at N, not at O, 3 coordinate N: CHEM 114 Fundamental Chemistry

  5. Tricoordinate nitrogen 5 electrons in 4 sp3 orbitals Start with 2s2 2p3 Promote to 2s1 2p4 3 electrons in 3 sp2 orbitals 2 electrons in 2pz 3 bonding sp3 orbitals + 1 lone pair NH3 NF3 CHEM 114 Fundamental Chemistry 3 bonding sp2 orbitals + 2 electrons in 2pz Two views of HNO3

  6. Electrode potential and nitrogen oxidation state CHEM 114 Fundamental Chemistry

  7. Ammonia CHEM 114 Fundamental Chemistry

  8. Phosphorus White phosphorus Red phosphorus Violet phosphorus and black phosphorus also exist CHEM 114 Fundamental Chemistry

  9. Phosphorus oxides and oxyacids Phosphorus has two valence states –3 under reducing conditions (e.g. PH3) +3 and +5 under oxidizing conditions (e.g. PCl3, PCl5) CHEM 114 Fundamental Chemistry

  10. Arsenic, antimony, bismuth • Elemental arsenic has three allotropes • Yellow arsenic, As4, structure like white phosphorus, but more unstable • Grey arsenic, structure like black phosphorus (2D network solid) • Black arsenic, structure like red phosphorus (1D network solid) Oxides: As2O3 and As2O5. Both are acidic, and react with water to give arsenous and arsenic acid (H3AsO3 and H3AsO4) Halides: AsF3, AsCl3, AsBr3, AsI3, AsF5. AsH3 (arsine) is pyrophoric • Elemental antimony has one stable and three unstable allotropes. • Metallic antimony is a shiny, brittle metal • Explosive antimony — well, what more can I add? • Black antimony (red phosphorus structure) slowly converts to the metal • Yellow antimony slowly converts to black antimony • Sb4 exists only in the liquid and gas state Oxides: Sb4O6 and Sb4O10. Sb4O10 is less stable. Sb(OH)3 converts back to the oxide Halides: SbF3, SbCl3, SbBr3, SbI3, SbF5, SbCl5. SbH3 (stibine) is very unstable. CHEM 114 Lecture 24 3/9/2011 One metallic bismuth allotrope Oxides: Bi2O3 only. Bi(H2O)63+ formed from Bi3+ in aqueous solution (strong Lewis acid) Halides: BiF3, BiCl3, BiBr3, BiI3, BiF5.

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