Atoms – the building blocks of matter University of Lincoln presentation This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
What’s so special about atoms? • All matter is made of atoms • When 2 surfaces touch each other, atoms from one surface are transferred to the other TRACE EVIDENCE This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
The Locard Principle of Exchange Prof Edmond Locard (18771966) “When objects come into contact there is a transfer of particles”……. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
For example • FIREARM DISCHARGE RESIDUE – When a firearm is discharged, traces of lead, antimony and barium are deposited onto the hand holding the gun. • IDENTIFYING SITE OF BULLET PENETRATION – 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 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
What you Need to Know… • Structure of the atom – proton, neutron and electron • Electron orbitals – s- and p-orbitals, principal quantum numbers and energy • Electronic configurations – noble gas configurations, core electrons and valence electrons • Drawing energy level diagrams – putting electrons into orbitals and pairing electrons This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Atomic Structure Direction of electron motion Electron Nucleus The Bohr atom This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Make-up of the Atom The NUCLEUS Two particles make up the nucleus: o PROTON o NEUTRON A third particle, the ELECTRON, moves around the nucleus in ORBITALS This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
The three atomic particles PROTON Charge (C) Charge number Rest mass (kg) Relative mass NEUTRON ELECTRON +1. 602 x 10 -19 0 -1. 602 x 10 -19 +1 0 -1 1. 673 x 10 -27 1. 675 x 10 -27 9. 109 x 10 -31 1837 1839 1 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Orbitals Consider the moon orbiting the earth: We always know where the moon is because we can see it – its position and motion can be defined EXACTLY 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. This is known as Heisenberg’s uncertainty principle This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Orbitals 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 Probabilities are calculated mathematically, and in this case are defined by the Schrödinger wave equation This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Why do we need to know where the electrons are? Element Matter made up of identical atoms Atoms Protons Neutrons The element is defined by the number of protons it has Electrons The number of electrons = the number of protons Position of the electrons within the atom defines the chemistry of the element This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Periodic Table of the Elements Hydrogen and s – block elements H Li p – block elements He d – block elements B Na Mg K Ca Sc Ti V Rb Sr Y Zr Nb Mo Tc Cs Ba La Hf Ta W Fr Ra Mn Fe Ce Th N O F Ne Si P S Cl Ar Ac Lanthanoids Actinoids Cr C Al Be Co Ni Cu Zn Ga Ge As Se Br Kr Ru Rh Pd Ag Cd In Sn Sb Te I Xe Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Pa U Np Pu Am Cm Cf Es Fm Md No Lr Bk f - block elements This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
The first 20 elements Element Number of protons (Atomic number = Z) Number of electrons H 1 1 Na 11 11 He 2 2 Mg 12 12 Li 3 3 Al 13 13 Be 4 4 Si 14 14 B 5 5 P 15 15 C 6 6 S 16 16 N 7 7 Cl 17 17 O 8 8 Ar 18 18 F 9 9 K 19 19 Ne 10 10 Ca 20 20 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Where are these electrons? According to Schrödinger, there are 4 different types of orbital in an atom (each type has a different shape): Orbital label No. orbitals No. e-s per orbital s p 1 3 2 2 2 6 d 5 2 10 f 7 2 14 Total no. e-s This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Shapes of Orbitals (s & p) S-orbital P-orbitals Px Py Pz This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Shapes of Orbitals (d) dyz dxy dxz Note change of axis dz 2 dx 2 y 2 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Electron Orbitals 1 s 2 s 3 s 4 s 5 s 6 s 2 p 3 p 4 p 5 p 6 p 3 d 4 d 5 d 4 f 5 f The number is called the principal quantum number (n) and indicates the size of the orbital (1 is the smallest; 7 the largest) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License 7 s
The Principal Quantum Number 1 s 2 s 3 s 4 s The increase in size of atomic orbitals This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Position of Orbitals Around Nucleus 4πr 2 R(r)2 Energy increase 1 s 2 s 3 s Nucleus This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Energy, E Relationship Between Principal Quantum Number and Energy 0 n=∞ n=6 n=5 n=4 n=3 Energy levels become closer together n=2 n=1 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Comparing the Energy for n=3 4πr 2 R(r)2 3 d Energy increase 3 p 3 s This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Energy The Energy of Orbitals 3 d 3 p N=3 3 s 2 p N=2 N=1 2 s 1 s Link to “Energy level diagrams” video Each orbital will hold 2 electrons This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
How do the electrons fill these orbitals? Groundstate electronic configurations: 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 The electrons will therefore occupy the lowest energy orbitals available This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Orbitals in energy order 1 s 2 s 3 s 4 s 5 s 6 s 2 p 3 p 4 p 5 p 6 p 3 d 4 d 5 d 4 f 7 s 5 f 1 s < 2 p< 3 s < 3 p < 4 s < 3 d < 4 p < 5 s < 4 d < 5 p< 6 s < 4 f 5 d < 6 p < 7 s < 5 f This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Electronic Configuration Atomic number Element Symbol Electronic configuration 1 H 1 s 1 11 Na 1 s 22 p 63 s 1 2 He 1 s 2 12 Mg 1 s 22 p 63 s 2 3 Li 1 s 22 s 1 13 Al 1 s 22 p 63 s 23 p 1 4 Be 1 s 22 s 2 14 Si 1 s 22 p 63 s 23 p 2 5 B 1 s 22 p 1 15 P 1 s 22 p 63 s 23 p 3 6 C 1 s 22 p 2 16 S 1 s 22 p 63 s 23 p 4 7 N 1 s 22 p 3 17 Cl 1 s 22 p 63 s 23 p 5 8 O 1 s 22 p 4 18 Ar 1 s 22 p 63 s 23 p 6 9 F 1 s 22 p 5 19 K 1 s 22 p 63 s 23 p 64 s 1 10 Ne 1 s 22 p 6 20 Ca 1 s 22 p 63 s 23 p 64 s 2 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Three things to remember 1. For principal quantum numbers >1 there is both an s- and a porbital. 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 2. CORE electrons are those electrons sitting in filled orbitals. These usually correspond to the noble gas configurations (He, Ne, Ar etc. ) 3. VALENCE electrons are the electrons outside the core electrons. It is these electrons that define the chemistry of the element This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
H Li He B Na Mg K Ca Sc Ti V Cr Mn Fe Rb Sr Y Zr Nb Mo Tc Cs Ba La Hf Ta W Fr Ra Th N O F Ne Si P S Cl Ar Ac Ce C Al Be Co Ni Cu Zn Ga Ge As Se Br Kr Ru Rh Pd Ag Cd In Sn Sb Te I Xe Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Pa U Np Pu Am Cm Cf Es Fm Md No Noble gases: All orbitals are filled Noble gases: Group 18 Lr Bk This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Energy Level Diagrams Arrangement of Electrons in Orbitals 2 p 2 s 1 s He Energy C Energy Work out the number of electrons that are present, and then start filling the lowest energy orbitals first 1 s Li 2 s 1 s Electrons remain unpaired when they can (i. e. when there is more than 1 orbital of the same energy) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
How do electrons pair up? Incorrect Correct In order to pair up, electrons have to spin in different directions = +ve spin = -ve spin This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Summary • Structure of the atom – proton, neutron and electron • Electron orbitals – s- and p-orbitals, principal quantum numbers and energy • Electronic configurations – noble gas configurations, core electrons and valence electrons • Drawing energy level diagrams – putting electrons into orbitals and pairing electrons This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
Acknowledgements • • JISC HEA Centre for Educational Research and Development School of natural and applied sciences School of Journalism Siren. FM http: //tango. freedesktop. org This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2. 0 UK: England & Wales License
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