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Elements, Ions & Isotopes

Elements, Ions & Isotopes. University of Lincoln presentation. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License. What you should know…. Elements and their classification Atoms/molecules Symbols of the elements Allotropy

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Elements, Ions & Isotopes

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  1. Elements, Ions & Isotopes University of Lincoln presentation This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  2. What you should know… • Elements and their classification • Atoms/molecules • Symbols of the elements • Allotropy • The Octet rule • Ions – cations/anions • Oxidation/reduction • Ionisation energy/electron affinity • Isotopes • Atomic mass • Relative atomic mass This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  3. 1. Elements This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  4. IUPAC Definition An element is matter, all of whose atoms are alike in having the same positive charge on the nucleus International Union of Pure and Applied Chemistry This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  5. Dictionary Definition A substance that cannot be decomposed into simpler substances This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  6. Are all elements simply collections of atoms? YES, normally Elemental mercury (liquid), Hg Elemental copper, Cu Elemental helium (gas), He Elemental gold, Au This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  7. Some elements only exist as molecules These elements exist as diatomic molecules* * A molecule is two or more atoms bonded together O2 H2 N2 Br2 Cl2 F2 I2 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  8. A = MASS NUMBER Z = ATOMIC NUMBER =number of protons N =number of neutrons A = N + Z X Symbols A Z This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  9. For Example H 1 Na 22 1 Ca 40 11 20 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  10. Classification of elements • Metals • Non-metals • Semi-metals This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  11. Classification of elements Metals Non-Metals H He B Li Be C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Semi-metals 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 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  12. Allotropes Some elements exist in more than one structural form. This property is called ALLOTROPY Consider carbon – 2 common allotropes are graphite and diamond. Both consist only of atoms of carbon, C, but their structures are very different, and hence their properties differ This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  13. Allotropes of Carbon Graphite layered structure C60 fullerene structure Diamond structure This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  14. Allotropes of other elements? • Tin, Sn • Phosphorus, P • Arsenic, As • Oxygen, O • Sulphur, S • Selenium, Se This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  15. 2. Ions This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  16. The Octet Rule Because filled orbitals give the best STABILITY, all elements try to attain a noble gas configuration (i.e. 8 electrons in their valence shell) 2 ways of doing this: (i) losing electrons; or (ii) gaining electrons (which ever uses the least energy) This is the driving force behind the chemistry of the elements and is called theOCTET RULE This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  17. The Periodic Table ns2np3 ns2np4 ns2np2 ns2np6 ns2np1 ns2np5 ns1 ns2 Hydrogen and s – block elements p – block elements n=1 H He d – block elements n=2 B Li Be C N O F Ne n=3 Na Mg Al Si P S Cl Ar n=4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr n=5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe n=6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn n=7 f - block elements Fr Ra Ac Lanthanoids Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Actinoids Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr The Periodic Table consists of rows of 8 elements (s + p block only) Each row corresponds to a different quantum number (n=1–7) Each column has the same VALENCE CONFIGURATION This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  18. Definition AnION is a charged atom or molecule. There are 2 types of ion: ACATIONis positively charged AnANIONis negatively charged This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  19. Cations • Cations are formed when an atom loses 1 or more valence electron: Na  Na++ e- Mg  Mg2++ 2e- • The loss of electrons is known as OXIDATION and is a typical reaction of metals This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  20. Valence Electrons This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  21. Group 1 & 2 elements (metals) Group 1Group 2 Group 1 = [NG]ns1 Group 2 = [NG]ns2 Elements in these groups want toLOSEtheir outer (valence) electrons to gain the noble gas configuration[NG]: Na  Na++ e- Mg  Mg2++ 2e- Electronic configuration of both cations = [Ne] The energy required to remove a valence electron is called theIONISATION ENERGY This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  22. Anions • Anions are formed when an atom gains 1 or more valence electron: F + e- F- O + 2e- O2- • The gain of electrons is known as REDUCTION and is a typical reaction of non-metals This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  23. Group 16 & 17 elements (non-metals) Groups 16 17 18 Group 16 = [NG]ns2np4 Group 17 = [NG]ns2np5 Elements in these groups want toGAINvalence electrons to attain the noble gas configuration[NG] ns2np6, which is the noble gas sitting on their RHS in the Periodic Table F + e-  F- O + 2e- O2- Electronic configuration of both anions = [Ne] Electron affinityis a measure of how easy it is to gain a valence electron This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  24. 3. Isotopes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  25. In 1913 Soddy proposed the existence ofISOTOPES Definition: Atoms of the same elements with different atomic masses Definition Frederick Soddy Nobel Prize (Chemistry) 1921 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  26. Definition Isotopes of an element have the same number of protons, but different numbers of neutrons Eg. 63 Mass number (A) Protons (Z) = 29 Neutrons (N) = 34 Cu 29 Atomic number (Z) 65 Protons (Z) = 29 Neutrons (N) = 36 Cu 29 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  27. Radioactivity discovered in 1896 Henri Becquerel Marie & Pierre Curie This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  28. Stable v. Radioactive Isotopes There are approximately 1,700 isotopes known to exist This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  29. Chart of the nuclides This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  30. Chart of the nuclides Z N Black squares denote STABLE isotopes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  31. Atomic Mass, A • For simplicity, atomic masses are given relative to the mass of 12C • 12C = 12.0000 amu • amu = atomic mass unit = 1.660x 10-27kg similar to the mass of a proton or neutron (see Lecture 1) Mass number (A) is used as the atomic mass This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  32. Relative Atomic Mass, Ar Atomic mass Mg 24 78.7 Mg 25 10.1 Mg 26 11.2 % abundance The relative atomic mass of an element is the weighted mean of the atomic masses of all the stable isotopes for that element. For example: Ar (Mg) = 24.3 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  33. Acknowledgements • JISC • HEA • Centre for Educational Research and Development • School of natural and applied sciences • School of Journalism • SirenFM • 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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