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CHAPTER 6: Periodic Table

CHAPTER 6: Periodic Table. Development of Periodic Table. Mendeleev Contributions – made very first periodic table p.t. arrangement: elements ordered by increasing atomic mass. Development of Periodic Table. 3) Noticed periodic pattern (repetition) in element properties

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CHAPTER 6: Periodic Table

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  1. CHAPTER 6:Periodic Table

  2. Development of Periodic Table • Mendeleev • Contributions – made very first periodic table • p.t. arrangement: elements ordered by increasing atomic mass

  3. Development of Periodic Table 3) Noticed periodic pattern (repetition) in element properties - elements placed in groups w/ similar properties - Left gaps for substances yet to be discovered

  4. Mendeleev’s Periodic Table (1871)

  5. 4) errors: when new elements discovered, several elements on his table didn’t fit right - had different properties

  6. Moseley • periodic table arrangement: elements ordered by increasing atomic number • Periodic Law – when elements arranged by increasing atomic number, their physical & chemical properties show a periodic pattern

  7. Modern Periodic Table • Boxes contain: • Element name • Element symbol • Atomic number • Atomic mass

  8. Modern Periodic Table • Arrangement – increasing atomic number a) groups – columns (vertical) b) periods – rows (horizontal)

  9. Two Divisions of Elements • Main Group Elements – groups 1A, 2A and 13-18A (s & p block)

  10. Two Division Of Elements • Transition Elements – group 3-12B elements (d block)

  11. Classifying Elements • Metals – elements w/ shine – solid @ room temp – conducts heat & electricity – malleable: put into thin wires – ductile: pound into sheets

  12. Metals a) Alkali Metals – group 1A (except H) - highly reactive, very soft b) Alkaline Earth Metals – group 2A - less reactive and denser than alkali metals c) Transition Metals – d-block (group 3-12B)

  13. Metals d) Inner transition metals – f-block i) Lanthanide Series – row 1 of f-block ii) Actinide Series – row 2 of f-block La Ac

  14. Nonmetals • Defn - gases or brittle, dull looking solids - poor conductors of heat & electricity a) Halogens b) Noble Gases - group 17A - highly reactive - group 18A - very unreactive/stable

  15. Metalloids • Defn – BORDER THE STAIRSTEP LINE  - Have similar chem & phys props as both metals and nonmetals

  16. Alkali metals Halogens Noble Gases Alkaline earth metals Transition Metals Lanthanides Actinides

  17. Organizing Elements By Electron Configuration • Valence Electron – electrons in highest energy level atoms in same group have similar chemical props b/c they have same # of valence e-

  18. Valence Electrons And Period • The period indicates what energy level the valence electrons are located on • Ex: [Ar] 4s2 3d10 4p1 3 Valence e- on 4th energy level

  19. Valence Electrons and Group Number • # of valence electrons equals group number (only for main group elements) • exception: Helium (in group 18, but has 2 valence e- only)

  20. Ex Problems • Tell the group, period, and block where these elements are located [Ne] 3s2 [He] 2s2 2p4 [Kr] 5s2 4d105p5 2 group – period – block – group – period – block – 16 group – period – block – 17 3 2 5 s p p

  21. Periodic Trends • There are certain patterns that occur with the elements as you go across and down the periodic table which atom is the biggest? smallest? which atom is most reactive/least stable?

  22. Atomic Radius (size) • Defn – distance from center to edge of electron cloud • Period Trend – decreases from left to right Why? increasing # of protons (+ charge) in nucleus has a greater attraction for electrons (- charge)

  23. Atomic Radius • Group Trend – increases from top to bottom Why? electrons occupy higher energy levels and are farther from the nucleus Period 1 Period 2 Period 3

  24. Atomic Radius • Summary decreases increases

  25. Ion • Defn – atom w/ a positive or negative charge - atom lost or gained electrons - # protons ≠ # electrons

  26. Cation • Defn – positive ion (atom lost e-) - more protons than electrons • Comparing atom size vs. its cation size A A+ atom A cation of atom A cations are SMALLER than its original atom

  27. Anion • Defn – negative ion (atom gained e-) - more electrons than protons • Comparing atom size vs. its anion size A- A atom A anion of atom A anions are LARGER than its original atom

  28. Ion Summary A- A A+ < < cation atom anion

  29. Ionization Energy • Defn – energy required to remove an electron from an atom • Period trend – IE increases from left to right Why? increased nucleus charge has greater hold on valence e-

  30. Ionization Energy • Group Trend – IE decreases from top to bottom Why? atomic size increases, valence e- are farther away so easier to remove (less energy required)

  31. Period 1 Period 2 Period 3

  32. Ionization Energy • Summary increases decreases

  33. Ex problem • Rank these atoms from increasing to decreasing ionization energy: Ba, Cs, Cl increases decreases Cl Cs Ba Cl > Ba > Cs

  34. Electronegativity • Defn – relative ability of an atom to attract electrons in a chemical bond “how badly does atom want electrons” while in a bond • Period Trend – increases from left to right • Group Trend – decreases from top to bottom

  35. Electronegativity • Summary increases decreases

  36. Ex problem • Rank these atoms from high to low electronegativity: O, Sr, Mg increases decreases Mg O Sr O > Mg > Sr

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