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Trends of the Periodic Table

Trends of the Periodic Table. Mrs. Nielsen Honors Chemistry. Dmitri Mendeleev Created the First Periodic Table. * Made index cards with element name, atomic mass, physical and chemical properties. * Arranged cards according to their properties, looked for trends and patterns.

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Trends of the Periodic Table

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  1. Trends of the Periodic Table Mrs. Nielsen Honors Chemistry

  2. Dmitri Mendeleev Created the First Periodic Table * Made index cards with element name, atomic mass, physical and chemical properties * Arranged cards according to their properties, looked for trends and patterns

  3. Mendeleev Published his Periodic Table in 1869 In Mendeleev’s version of the Periodic table, the elements are arranged in order of increasing ATOMIC MASS

  4. The Modern Periodic Table * Created by Henry Moseley in 1913 * Elements are arranged in order of increasing ATOMIC NUMBER according to the periodic law

  5. An arrangement of the elements in order of their ATOMIC NUMBERS so that elements with similar properties fall in the same column, or group. The Modern Periodic Table Periodic Law: The physical and chemical properties of the elements are periodic functions of their atomic numbers The Elements Song by Tom Lehrer

  6. What is a Trend? A predictable change in a particular direction Food for thought: What “trends” do you see at Mira Costa High School?

  7. A Key to the Trends Decreasing Down Increasing right Decreasing right Increasing Down

  8. Atomic Radius: The distance from the center of an atom's nucleus to its outermost electron. The Atomic Radius is measured by finding ½ the distance between the nuclei of two identical atoms bonded together (pm = picometers = 1x10-12m)

  9. Atomic Radius: The distance from the center of an atom's nucleus to its outermost electron. Across a period: Increased positive charge in the nucleus  decreases atomic radius (Coulomb’s Law) - Down a group: Electrons exist in higher energy levels  increasing atomic radius +

  10. Atomic Radius Practice Which has a greater Atomic Radius? • Carbon or Fluorine? • Phosphorus or Nitrogen? • Francium or Helium? Carbon Phosphorus Francium

  11. Ionization Energy (kJ/mol): The amount of energy required to remove 1 electron from the valence shell of an atom.

  12. Ionization Energy (kJ/mol): The amount of energy required to remove 1 electron from the valence shell of an atom. Ion: Atom or group of bonded atoms that have a + or – charge. Across a period: Increased positive charge in the nucleus  more difficult to remove the valence electrons (Coulomb’s Law) - Ionization: Process that forms an ion. Down a group: Electrons exist in higher energy levels and MORE shielding  valence e- further away from the nucleus, easier to remove e-. (Coulomb’s Law) + ex) Na  Na+ + 1 e- Ionization Energy

  13. Ionization Energy Practice Which has a greater Ionization Energy? • Aluminum or Chlorine? • Fluorine or Bromine? • Francium or Helium? Chlorine Fluorine Helium

  14. Valence Electrons * Electrons available to be lost, gained, or shared to form compounds and molecules * The electrons in the outermost energy level (shell) How many valence electrons do each of the following neutral elements have? K: 1  Loses 1 e- to form K+ Mg: 2  Loses 2 e- to form Mg+2 Al: 3  Loses 3 e- to form Al+3 S: 6  Gains 2 e- to form S-2

  15. Ionic Radius: An estimate of the size of an ion in an ionic compound; found from the internuclear distance.

  16. Ionic Radius

  17. Ionic Radius Cation= positively charged ion Anion = negatively charged ion 10 e- 2 e- 3 p+ 8 p+ ex) Lithium  Li+ ex) Oxygen  O-2 Cations will have a SMALLER atomic radius than the neutral atom. Anions will have a LARGER atomic radius than the neutral atom.

  18. Ionic Radius Practice N-3 Mg S-2 Which has a greater Ionic Radius? N or N-3? Mg or Mg+2? S or S-2?

  19. ElectronegativityThe ability of an atom in a chemical compound to attract electrons I am soooo electronegative… Wow, he is one attractive element…

  20. Speaking of Attraction… Playa Potrero, Costa Rica July 1, 2011

  21. And, a few more…

  22. Electronegativity: The ability of an atom in a chemical compound to attract electrons Across a period: Increasing positive nuclear charge “pulls” electrons in more - Down a group: Electrons exist in higher energy levels  force of attraction decreases with distance + FONClBrISCH

  23. Electronegativity Practice Which has a greater Electronegativity? • Potassium or Chlorine? • Fluorine or Bromine? • Francium or Sulfur? Chlorine Fluorine Sulfur

  24. Electronegativity and Polar Molecules Polar molecules have an uneven distribution of charge due to large differences in electronegativity. ex) H2O δ = greek symbol delta = “partial” δ+ ex) HF δ- Dipole Moment!

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