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Regents Chemistry

Regents Chemistry. Tyna L Meeks. Unit 5: Periodicity. Periodic Table - Organizes many “facts” and trends in chemical reactivity Based upon electronic configurations of the elements Similarities in electronic properties leads to similarities in chemical reactivity and structure.

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Regents Chemistry

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  1. Regents Chemistry Tyna L Meeks

  2. Unit 5: Periodicity • Periodic Table - Organizes many “facts” and trends in chemical reactivity • Based upon electronic configurations of the elements • Similarities in electronic properties leads to similarities in chemical reactivity and structure

  3. What does it mean to be Periodic? • Who created the first periodic table? • What did he use to organize the table? • Do we still use the same things?

  4. Unit 5: Periodicity • Element - a substance that cannot be decomposed into simpler substances by chemical or physical means. • Most elements not found in nature in “elemental” form but in combination with other elements (particularly H or O) in the form of minerals… SiO2, or PbO • Prior to 1800, 31 elements known (mostly those that were found in elemental form in nature (i.e., gold, silver, nitrogen, etc...).

  5. Periodic Table Development • Between 1800 and 1865, 32 more were isolated by improved chemical techniques. • Dmitri Mendeleev - noted that chemical and physical properties recur periodically when the elements are arranged in order of increasing atomic weight. (atomic number not known then although atomic weights generally follow atomic number sequence) • When he created the table, he was forced to leave blank spaces for “undiscovered” elements but he correctly predicted many of their properties by use of his table.

  6. Periodic Table Development

  7. Mendeleev’s Guesses Guesses for Ge based upon Periodic Trends Table in TEXT • Mendeleev’s guesses Observed for Ge (1871) properties for Ge (1886) Atomic Weight 72 72.59 Density 5.5 5.35 Specific Heat (J/gK) 0.305 0.309 Melting Point (°C) High 947 Oxide Formula XO2 GeO2 Density of Oxide 4.7 g/cm3 4.70 g/cm3 Chloride Formula XCl4 GeCl4 Chloride b.p. (°C) <100 84

  8. Mendeleev’s Guesses Guesses for Ge based upon Periodic Trends Table in TEXT • Mendeleev’s guesses Observed for Ge (1871) properties for Ge (1886) Atomic Weight 72 72.59 Density 5.5 5.35 Specific Heat (J/gK) 0.305 0.309 Melting Point (°C) High 947 Oxide Formula XO2 GeO2 Density of Oxide 4.7 g/cm3 4.70 g/cm3 Chloride Formula XCl4 GeCl4 Chloride b.p. (°C) <100 84

  9. Periodic Development • Moseley (1887-1915) discovered atomic number concept (atomic number = number or protons and electrons in an atom) from assigning X-ray from the elements. • Periodic Table: • column or groups (increasing n, principal quantum number, on descending G r o u p Period

  10. metals metalloids non-metals Metals, Nonmetals and Metalloids Nonmetallic Properties Increase Metallic Properties Increase

  11. Metals, Nonmetals and Metalloids metalsnon-metals Gold Graphite

  12. Metals

  13. Transition Metals

  14. Non Metals

  15. Metalloids

  16. Metals, Nonmetals and Metalloids metalsnon-metals conductors insulators shiny dull high thermal conductivity thermal insulators solids STP (except Hg) freq. non-solids at STP ductile and malleable brittle Metalloids (along line in table) have properties between metals and non-metals

  17. Group Trends: Group I (+1) Alkali Metals 7Li 3 23Na 11 39K 19 85Rb 37 133Cs 55 Li Na K 223Fr 87 MOST REACTIVE : http://youtu.be/m55kgyApYrY

  18. Group Trends: Group 2 (+2) Alkaline Earth Metals 9Be 4 24Mg 12 40Ca 20 87Sr 38 137Ba 56 Mg Ca 226Ra 88 MOST REACTIVE

  19. Group Trends: Group 13 (+3) Boron Family • Boron Compounds; Numerous Polyhedral Compounds (covalent) Boron Neutron Capture Therapy • Aluminum; 2Al + Fe2O3 Al2O3 + 2Fe THERMITE REACTION Gemstones; Al2O3 (Alumina) trace Cr+3 = ruby trace Fe+2, Fe+3, Ti+3 = blue sapphire 11B 5 27Al 13 70Ga 31 115In 49 204Tl 81 Uut 113

  20. Group Trends: Group 14 (+4/-4) Carbon Family • Carbon Compounds; ORGANIC – living things • Silicon 12C 6 28Si 14 73Ge 32 119Sn 50 206Pb 82 Uug 114

  21. Group Trends: Group 15 (-3) Nitrogen Family • Nitrogen Compounds; Nitrogen cycle • Phosphorous • Arsenic 14N 7 31P 15 75As 33 122Sb 51 209Bi 83

  22. Group Trends: Group 16 (-2) Chalcogens • Oxygen - two allotropes (allotropes - different form of the same element) - O2 and O3. • S reacts similarly to oxygen 16O 8 32S 16 79Se 34 128Te 52 209Po 84

  23. Group Trends: Group 17 (-1) Halogens • Greek for “salt formers”. • Diatomic in elemental state (F2, Cl2, Br2, etc...). 19F 9 35Cl 17 80Br 35 127I 53 210At 85

  24. Group Trends: Group I8 (0) Noble Gases 4He 2 20Ne 10 40Ar 18 83Kr 36 131Xe 54 222Rn 86

  25. What does it mean to be Periodic? • What THREE trends do we identify from the periodic table? • How does each trend get defined? • What happens in each trend as you go down a group? From left to right across the period?

  26. Periodic Table Atomic Radii The stronger the positively charged nucleus in an electron shell, the closer the electrons are attracted to the nucleus 2r 1. Radii increase from top to bottom within a group 2. Radii increase in moving R to L within a period Radius Increases

  27. Atomic Sizes • Li < Na < K < Rb < Cs due to additional shells of electrons • Li > F due to increasing positive nuclear charge values.. Rb K Transition Metals Na Transition Metals Li Atomic Radius (Å) I F Br Cl 10 20 30 40 50 Atomic Number

  28. Periodic Table Ionization Energies • Endothermic • Larger atoms require less energy to remove an electron from the valence shell • Smaller atoms require more energy to remove an electron from the valence shell 1st IE Increases

  29. Ionization Energies (IE) He Ne N F 1st IE (kJ/mol) H O Be C B Li Atomic Number

  30. Ionization Energy

  31. Ionization Energy

  32. Periodic Table Electronegativity • Scaled from 0-4 ; describes how badly an atom wants to gain an electron to fill its valence shell • Larger atoms have a more difficult time gaining an electron to fill the valence shell, lower scaled score • Smaller atoms have an easier time gaining an electron to fill the valence shell, higher scaled score Electronegativity increases

  33. Electronegativity F O N EN C B Be Li Atomic Number

  34. Electronegativity

  35. Metallic Properties

  36. In Conclusion

  37. What do the group numbers and period numbers tell us? • What do the group numbers represent? • Is there another way to draw this? • What do the period numbers represent?

  38. Group numbers… • Each group number is actually the number of valence electrons in the last shell of electrons • This helps us decide if we will lose or gain electrons and what the potential charge might be

  39. Valence Electrons… • Lewis Dot Structures

  40. Period numbers… • Each period number is actually the number of shells of electrons that can exist in that atom. • Each shell can only hold a certain number of atoms, the last shell is known as the valence shell • 1st = 2 electrons • 2nd = 8 electrons • 3rd = 18 electrons • 4th = 32 electrons • all inside shells are known as core shells

  41. Electron Arrangements

  42. Electron Arrangements

  43. Electron Arrangements

  44. Electron Arrangements

  45. Electron Arrangements

  46. Periodic Table s orbitals f orbitals p orbitals closed shell 2s 2p d orbitals 3s 3p 3d 4p 4s 4d 5s 5p 6s 6p 5d 7s 6d 4f 5f

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