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Periodic Trends

Periodic Trends. Atomic Radius. Definition: Half of the distance between nuclei in covalently bonded diatomic molecule . Radius decreases across a period Increased effective nuclear charge due to decreased shielding Radius increases down a group

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Periodic Trends

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  1. Periodic Trends

  2. Atomic Radius Definition: Half of the distance between nuclei in covalently bonded diatomic molecule • Radius decreases across a period • Increased effective nuclear charge due to decreased shielding • Radius increases down a group • Each row on the periodic table adds a “shell” or energy level to the atom

  3. Table of Atomic Radii

  4. Period Trend:Atomic Radius

  5. Definition: the energy required to remove an electron from an atom Ionization Energy • Increases for successive electrons taken from the same atom • Tendsto increase across a period • Electrons in the same quantum level do not shield as effectively as electrons in inner levels • Irregularities at half filled and filled sublevels due to extra repulsion of electrons paired in orbitals, making them easier to remove • Tends to decrease down a group • Outer electrons are farther from the nucleus and easier to remove

  6. Ionization Energy: the energy required to remove an electron from an atom • Increases for successive electrons taken from the same atom • Tends to increase across a period Electrons in the same quantum level do not shield as effectively as electrons in inner levels Irregularities at half filled and filled sublevels due to extra repulsion of electrons paired in orbitals, making them easier to remove • Tends to decrease down a group Outer electrons are farther from the nucleus

  7. Table of 1st Ionization Energies

  8. Periodic Trend:Ionization Energy

  9. Electron Affinity Definition - the energy change associated with the addition of an electron • Affinity tends to increase across a period • Affinity tends to decrease as you go down in a period Electrons farther from the nucleus experience less nuclear attraction Some irregularities due to repulsive forces in the relatively small p orbitals

  10. Periodic Trend:Electron Affinity

  11. Electronegativity Definition: A measure of the ability of an atom in a chemical compound to attract electrons • Electronegativity tends to increase across a period • As radius decreases, electrons get closer to the bonding atom’s nucleus • Electronegativity tends to decrease down a group or remain the same • As radius increases, electrons are farther from the bonding atom’s nucleus

  12. Periodic Table of Electronegativities

  13. Periodic Trend:Electronegativity

  14. Summary of Periodic Trends

  15. Ionic Radii • Positively charged ions formed when • an atom of a metal loses one or • more electrons Cations • Smaller than the corresponding • atom • Negatively charged ions formed • when nonmetallic atoms gain one • or more electrons Anions • Larger than the corresponding • atom

  16. Table of Ion Sizes

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