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Chapter 5

Chapter 5. The Periodic Law. History. Cannizzaro - 1860 presented a new method for determining mass of elements gave scientists a way to organize elements . History. Mendeleev -Russian 1869 organized elements according to mass and properties

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Chapter 5

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  1. Chapter 5 The Periodic Law

  2. History • Cannizzaro- 1860 • presented a new method for determining mass of elements • gave scientists a way to organize elements

  3. History • Mendeleev-Russian 1869 • organized elements according to mass and properties • noticed that properties repeated periodically • predicted elements, later identified as Sc,Ga,Ge

  4. History • Moseley-1911 • Used X-rays for determining the # of protons • This is how our current periodic table is arranged.

  5. Periodic Law • Physical and chemical properties repeat periodically if arranged according to atomic number. Recurring or reappearing from time to time; intermittent. http://www.thefreedictionary.com • Look for overall patterns- may see some variation.

  6. History • Changes since Moseley • Noble gases-Ramsay • Lanthanides/Actinides- Seaborg

  7. The Periodic Table Trends

  8. Atomic Radius • tells us the size of the atom • measured using ½ the distance between the nuclei of identical atoms bonded together

  9. Atomic Radius • TREND: • going across the atoms get smaller • going down the atoms get larger

  10. Ionic Radius • tells us the size of the ion • positive or negative atom because of loss or gain of electrons • Cation-positive ion • Anion-negative ion

  11. Ionic Radius • Cations are smaller than the parent • Lose electrons

  12. Ionic Radius • Anions are larger than the parent. • Gain electrons.

  13. Ion Formation • Why do ions form? • Atoms try to become stable. • Achieve a noble gas configuration. • Become isoelectronic with noble gases • Having the same electron configuration

  14. Ion Formation • Examples: • Calcium • Nitrogen

  15. Ion Formation • You try these: • Potassium • Iodine • Aluminum

  16. Ionization Energy • Amount of energy required to remove an electron from an atom

  17. Electron Affinity • energy change when an electron is added to an atom • energy release means it is easier to add e- • opposite of ionization energy

  18. Electronegativity • measure of the ability of an atom to attract electrons when it is bonded to another atom • Think: sharing with a partner, equal sharing or unequal sharing

  19. Table of Electronegativities

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