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Periodic Trends

Periodic Trends. Usually Refers to Main Group Elements Only!. Atomic Size. As you move down a group, atomic radii increases WHY? As the number of energy levels increases, each energy level is further from the nucleus. Atomic Size. Atomic Size.

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Periodic Trends

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  1. Periodic Trends Usually Refers to Main Group Elements Only!

  2. Atomic Size • As you move down a group, atomic radii increases • WHY? • As the number of energy levels increases, each energy level is further from the nucleus

  3. Atomic Size

  4. Atomic Size • As you move across a period, atomic size decreases. • WHY? • As you go across, electrons are added to the same energy level as protons are added to the nucleus • Therefore there is a stronger force of attraction pulling the electrons closer to the nucleus

  5. Atomic Size

  6. Ionic Size • Anions (negative ions) are larger than their respective atoms. • WHY? • Electrons outnumber protons, the protons cannot pull the extra electrons as tightly toward the nucleus

  7. Ionic Size • Cations (positive ions) are smaller than their respective atoms • WHY? • Protons outnumber electrons and can pull the fewer electrons more closely to the nucleus • If the electron(s) lost are the only valence electron(s), the entire energy level is lost.

  8. Ionization Energy • The energy required to remove the outermost electron from a neutral atom • As you move down a group, IE decreases. • WHY? • Electrons are further from the nucleus and thus easier to remove.

  9. Ionization Energy • As you move across a period, IE increases • WHY? • As you move across, atomic radius decreases, the outer electrons are closer to the nucleus and more strongly attracted; therefore, harder to remove.

  10. Ionization Energy

  11. Ionization Energy • Element 1st IE 2nd IE 3rd IE • Na 495 4562 6912 • Mg 737 1450 7732 • Al 577 1816 2744

  12. Valence Electrons • As you move down a group, valence electrons remain the same • As you move across a period, valence electrons increase

  13. Electronegativity • The measure of the ability of an atom to attract electrons. • As you move across a period, electronegativity increases. • WHY? • Atomic radius decreases as you move across the period. Smaller atoms have a stronger force of attraction for its own electrons and for other atoms’ electrons.

  14. Electronegativity • As you move down a group, electronegativity decreases. • WHY? • There is an increased distance between the valence electrons and the nucleus.

  15. Summary of the Trends • Moving Left --> Right • Atomic Size Decreases • Ionization Energy Increases • Electronegativity Increases • Nonmettalic Properties Increase

  16. Summary of the Trends • Moving Top --> Bottom • Atomic Size Increases • Ionization Energy Decreases • Electronegativity Decreases • Metallic Properties Increase

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