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

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

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”…….

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

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

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. 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. 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

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. 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. 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. 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. 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. 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. 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. 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

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. 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

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. 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. 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