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Chemical Structure: Structure of Matter. Atoms – the building blocks of matter

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Lecture materials for the Introductory Chemistry course for Forensic Scientists, University of Lincoln, UK. See http://forensicchemistry.lincoln.ac.uk/ for more details.

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Chemical Structure: Structure of Matter. Atoms – the building blocks of matter

  1. 1. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Atoms – the building blocks of matter University of Lincoln presentation
  2. 2. What’s so special about atoms? <ul><li>All matter is made of atoms </li></ul><ul><li>When 2 surfaces touch each other, atoms from one surface are transferred to the other </li></ul><ul><li>TRACE EVIDENCE </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  3. 3. The Locard Principle of Exchange This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Prof Edmond Locard (1877-1966) “ When objects come into contact there is a transfer of particles”…….
  4. 4. For example <ul><li>FIREARM DISCHARGE RESIDUE </li></ul><ul><li>– When a firearm is discharged, traces of lead, antimony and barium are deposited onto the hand holding the gun. </li></ul><ul><li>IDENTIFYING SITE OF BULLET PENETRATION </li></ul><ul><li>– Uncoated lead bullets and copper-coated bullets discharged from firearms and penetrating wood, fabric, paper, etc., leave behind 0.1 – 100 micron particles of metallic lead or copper </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  5. 5. What you Need to Know… <ul><li>Structure of the atom – proton, neutron and electron </li></ul><ul><li>Electron orbitals – s- and p-orbitals, principal quantum numbers and energy </li></ul><ul><li>Electronic configurations – noble gas configurations, core electrons and valence electrons </li></ul><ul><li>Drawing energy level diagrams – putting electrons into orbitals and pairing electrons </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  6. 6. Atomic Structure This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License The Bohr atom Direction of electron motion Nucleus Electron
  7. 7. Make-up of the Atom <ul><li>The NUCLEUS </li></ul><ul><li>Two particles make up the nucleus: </li></ul><ul><li>PROTON </li></ul><ul><li>NEUTRON </li></ul><ul><li>A third particle, the ELECTRON , moves around the nucleus in ORBITALS </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  8. 8. The three atomic particles This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 1 1839 1837 Relative mass 9.109x10 -31 1.675x10 -27 1.673x10 -27 Rest mass (kg) -1 0 +1 Charge number -1.602x10 -19 0 +1.602x10 -19 Charge (C) ELECTRON NEUTRON PROTON
  9. 9. Orbitals <ul><li>Consider the moon orbiting the earth: </li></ul><ul><li>We always know where the moon is because we can see it – its position and motion can be defined EXACTLY </li></ul><ul><li>For an e - with a tiny mass, this is not the case – it is impossible to know, exactly, both its position and momentum at the same instant in time. </li></ul><ul><li>This is known as Heisenberg’s uncertainty principle </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  10. 10. Orbitals <ul><li>If we can’t determine exactly where the electron is, we must consider the probability of finding the electron in a given volume of space. This volume of space is called an ORBITAL </li></ul><ul><li>Probabilities are calculated mathematically, and in this case are defined by the </li></ul><ul><li>Schr ödinger wave equation </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  11. 11. Why do we need to know where the electrons are? This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Element Matter made up of identical atoms Atoms Protons Neutrons Electrons The element is defined by the number of protons it has The number of electrons = the number of protons Position of the electrons within the atom defines the chemistry of the element
  12. 12. Periodic Table of the Elements This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License f - block elements H Be Li Na K Rb Cs Fr Mg Ca Sr Ba Ra Sc Y La Ac Ti V Cr Mn Fe Co Ni Cu Zn Zr Hf Ta W Re Os Ir Pt Au Hg Tl Nb Mo Tc Ru Rh Pd Ag Cd In Sn Pb Bi Po At Rn Xe Kr Ar Ne Sb Te I Ga Al Ge Si P S Cl As Se Br Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr He B C N O F Lanthanoids Actinoids d – block elements Hydrogen and s – block elements p – block elements
  13. 13. The first 20 elements This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Number of electrons Number of protons (Atomic number = Z) Element 20 20 Ca 19 19 K 18 18 Ar 17 17 Cl 16 16 S 15 15 P 14 14 Si 13 13 Al 12 12 Mg 11 11 Na 9 9 F 10 10 Ne 8 8 O 7 7 N 6 6 C 5 5 B 4 4 Be 3 3 Li 2 2 He 1 1 H Number of electrons Number of protons (Atomic number = Z) Element
  14. 14. Where are these electrons ? <ul><li>According to Schr ödinger, t here are 4 different types of orbital in an atom (each type has a different shape ): </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 14 2 7 f 10 2 5 d 6 2 3 p 2 2 1 s Total no. e - s No. e - s per orbital No. orbitals Orbital label
  15. 15. Shapes of Orbitals (s & p) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License S-orbital P-orbitals P x P y P z
  16. 16. Shapes of Orbitals (d) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License d yz d xy d xz d z 2 d x 2 y 2 Note change of axis
  17. 17. Electron Orbitals This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License The number is called the principal quantum number ( n ) and indicates the size of the orbital (1 is the smallest; 7 the largest) 5f 4f 5d 4d 3d 6p 5p 4p 3p 2p 7s 6s 5s 4s 3s 2s 1s
  18. 18. The Principal Quantum Number This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 1 s 2 s 3 s 4 s The increase in size of atomic orbitals
  19. 19. Position of Orbitals Around Nucleus This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Nucleus 4 π r 2 R(r) 2 1s 2s 3s Energy increase
  20. 20. Relationship Between Principal Quantum Number and Energy This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Energy, E 0 n = 1 n = 2 n = 3 n = 4 n = 5 n = 6 n = ∞ Energy levels become closer together
  21. 21. Comparing the Energy for n=3 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 3d 3p 3s 4 π r 2 R(r) 2 Energy increase
  22. 22. The Energy of Orbitals This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Energy 1 s 2 s 3 s 2 p 3 p 3 d N = 1 N = 2 N = 3 Each orbital will hold 2 electrons Link to “Energy level diagrams” video
  23. 23. How do the electrons fill these orbitals? <ul><li>Groundstate electronic configurations: </li></ul><ul><li>In order for an element to be stable , it has to house its electrons in such a way that its overall energy is as low as possible </li></ul><ul><li>The electrons will therefore occupy the lowest energy orbitals available </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  24. 24. Orbitals in energy order This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 1s < 2s < 2p< 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p< 6s < 4f  5d < 6p < 7s < 5f 5f 4f 5d 4d 3d 6p 5p 4p 3p 2p 7s 6s 5s 4s 3s 2s 1s
  25. 25. Electronic Configuration This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 Ca 20 1s 2 2s 2 2p 6 Ne 10 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 K 19 1s 2 2s 2 2p 5 F 9 1s 2 2s 2 2p 6 3s 2 3p 6 Ar 18 1s 2 2s 2 2p 4 O 8 1s 2 2s 2 2p 6 3s 2 3p 5 Cl 17 1s 2 2s 2 2p 3 N 7 1s 2 2s 2 2p 6 3s 2 3p 4 S 16 1s 2 2s 2 2p 2 C 6 1s 2 2s 2 2p 6 3s 2 3p 3 P 15 1s 2 2s 2 2p 1 B 5 1s 2 2s 2 2p 6 3s 2 3p 2 Si 14 1s 2 2s 2 Be 4 1s 2 2s 2 2p 6 3s 2 3p 1 Al 13 1s 2 2s 1 Li 3 1s 2 2s 2 2p 6 3s 2 Mg 12 1s 2 He 2 1s 2 2s 2 2p 6 3s 1 Na 11 1s 1 H 1 Electronic configuration Element Symbol Atomic number Electronic configuration Element Symbol Atomic number
  26. 26. Three things to remember <ul><li>1. For principal quantum numbers >1 there is both an s- and a p-orbital. This means 8 electrons are needed to fill these two orbitals. If the orbitals are all filled, the element is extra stable. These elements are the NOBLE gases </li></ul><ul><li>2. CORE electrons are those electrons sitting in filled orbitals. These usually correspond to the noble gas configurations (He, Ne, Ar etc.) </li></ul><ul><li>3. VALENCE electrons are the electrons outside the core electrons. It is these electrons that define the chemistry of the element </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  27. 27. Noble gases: Group 18 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Noble gases: All orbitals are filled H Be Li Na K Rb Cs Fr Mg Ca Sr Ba Ra Sc Y La Ac Ti V Cr Mn Fe Co Ni Cu Zn Zr Hf Ta W Re Os Ir Pt Au Hg Tl Nb Mo Tc Ru Rh Pd Ag Cd In Sn Pb Bi Po At Rn Xe Kr Ar Ne Sb Te I Ga Al Ge Si P S Cl As Se Br Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr He B C N O F
  28. 28. Energy Level Diagrams - Arrangement of Electrons in Orbitals This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Electrons remain unpaired when they can (i.e. when there is more than 1 orbital of the same energy) Work out the number of electrons that are present, and then start filling the lowest energy orbitals first Energy 1 s 2 s C He Li Energy 1 s 2 s 2 p Energy 1 s
  29. 29. How do electrons pair up? This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License In order to pair up, electrons have to spin in different directions = +ve spin = -ve spin Incorrect Correct
  30. 30. Summary <ul><li>Structure of the atom – proton, neutron and electron </li></ul><ul><li>Electron orbitals – s- and p-orbitals, principal quantum numbers and energy </li></ul><ul><li>Electronic configurations – noble gas configurations, core electrons and valence electrons </li></ul><ul><li>Drawing energy level diagrams – putting electrons into orbitals and pairing electrons </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  31. 31. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Acknowledgements <ul><li>JISC </li></ul><ul><li>HEA </li></ul><ul><li>Centre for Educational Research and Development </li></ul><ul><li>School of natural and applied sciences </li></ul><ul><li>School of Journalism </li></ul><ul><li>SirenFM </li></ul><ul><li>http:// tango.freedesktop.org </li></ul>

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