1. Reaction rates are influenced by A.activation energy B.temperature C.relative abundance of reactants D.all of the above Monday’s Unregister ed clickers: 1B37B39F 1B462578 1B3E85A0

2. Catalysts speed up reactions but are not used up A.true B.false

3. Catalysts work by A.lowering the activation energy. B.orienting molecules (reactants) in the right way so they can react. C.Sometimes 1 and sometimes 2, depending on the reaction.

4. reduce activation energy correct orientation the right orientation

5. Chemical reactions happen in order to A.increase entropy B.decrease energy C.some combination of 1 and 2

6. What are these bonds like? How does the wave model explain all this? Bonding in Metals, Alloys, and Semiconductors

7. Metals Non-Metals Semiconductor (near the dividing line)

8. sp d f

9. metals bonding deals with the valence electrons. metals have mostly empty orbitals. metals have low ionization energies electrons want to be in the lowest possible energy states s p d f

10. metals bonding deals with the valence electrons. metals have mostly empty orbitals. metals have low ionization energies electrons want to be in the lowest possible energy states When 2 atoms get close together, new molecular orbitals form 2 atoms and the wave model two separated atoms two atoms in a molecule

11. 3 atoms… When 2 atoms get close together, new molecular orbitals form 2 atoms and the wave model two separated atoms two atoms in a molecule three separated atoms three atoms in a molecule

12. 3 atoms… energy of molecular orbitals overlap ENERGY BANDS a jillion atoms energy bands in a solid three separated atoms three atoms in a molecule valence band conduction band

13. bands with overlapping energies bands not completely full METALS energy of molecular orbitals overlap ENERGY BANDS a billion atoms energy bands in a solid valence band conduction band valence band conduction band

14. bands with overlapping energies bands not completely full METALS orbitals smeared out in energy AND space “electron glue” fills in the gaps between atoms non-locality valence band conduction band

15. metals are… –malleable –electrical conductors –thermal conductors –opaque –reflective Metallic properties orbitals smeared out in energy AND space “electron glue” fills in the gaps between atoms non-locality Most also melt at higher temperatures

16. metals are… –malleable –electrical conductors –thermal conductors –opaque –reflective Metallic properties When the metal is deformed, the electrons move. malleable Many also melt at high temperatures

17. push electrons into one side of the metal, and some electrons squeeze out the other side. good conductors When the metal is deformed, the electrons move. malleable

18. According to the wave model of the atom, how does a single atom absorb a photon? A.An atom can absorb light of any wavelength. B.An atom absorbs light when the photon energy equals the energy difference between orbitals. C.An atom changes its internal state to match the photon energy.

19. For visible light, there are MANY empty orbitals. The metal absorbs a photon and an electron jumps up to an un-filled orbital opaque The excited electron falls back down to the lowest possible energy state It emits a photon like the one it absorbed reflective photon in electron excited electron falls photon emitted

20. Near the boundary between metals and non-metals semiconductors The excited electron falls back down to the lowest possible energy state It emits a photon like the one it absorbed reflective electron falls photon emitted

21. Near the boundary between metals and non-metals semiconductors Conduction and valence bands do not overlap Band Gap valence band conduction band band gap

22. For a small band gap, a few electrons go into the conduction band Adjust the size of the band gap by doping Doping: add a few atoms Small Gap: Semiconductor Impurity atoms stress the network Stresses change energy levels and band gap Different Gap: different colors Doping

23. For a small band gap, a few electrons go into the conduction band Adjust the size of the band gap by doping Doping: add a few atoms Small Gap: Semiconductor Conduction and valence bands do not overlap Band Gap valence band conduction band band gap

24. atoms and electrons have different speed distributions Thermal Excitation Impurity atoms stress the network Stresses change energy levels and band gap Different Gap: different colors Doping atoms electrons valence band conduction band gap