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Periodic Properties of the Elements

Periodic Properties of the Elements. CHM 108 Suroviec Spring 2014. I. Development of the Periodic Table. The modern periodic table is credited to Dmitri Mendeleev Table is based on the periodic law. II. Electron Configuration.

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Periodic Properties of the Elements

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  1. Periodic Properties of the Elements CHM 108 Suroviec Spring 2014

  2. I. Development of the Periodic Table • The modern periodic table is credited to Dmitri Mendeleev • Table is based on the periodic law

  3. II. Electron Configuration • Quantum Mechanical Theory describes the behavior of electrons in atoms.

  4. A. Electron Spin and the Pauli Exclusion Principle • Electron configurations can also be represented in an orbital diagram • In an orbital diagram the direction of the arrow shows the electron spin

  5. number of electrons in the orbital or subshell principal quantum number n angular momentum quantum number l 1s1 Orbital diagram 1s1 Orbital diagram H

  6. B. Multi-electron atoms • In H and He the energy of the orbital depends only on principle quantum number • For atoms with more than 2 electrons, the energy depends on l & n

  7. Example • Lithium • Magnesium • What are the possible quantum numbers for the last (outermost) electron in Cl?

  8. C. Electron configuration of multi-electron atoms • Now that we know the energy of orbitals we can build ground state electron configuration for other elements. • We use Hund’s rule of filling degenerate orbitals to fill them singly with up spin first

  9. Hund’s Rule

  10. III. Electron Configuration, Valence Electrons and the Periodic Table • The highest principle number increases by 1 going down a row • As you move across a row the number of electrons increases by 1 in the outer most energy level.

  11. IV. QM Model Explains Ions • A all atoms in a column will have the same number of valence electrons

  12. V. Periodic Variations of Physical Properties • The chemical and physical properties of elements are a periodic function of atomic number • Recall that the number of electrons is equal to the atomic number of an element • Properties to be considered • Atomic Radius (and Ionic Radius) • Effective Nuclear Charge • Ionization Energy • Electron Affinity

  13. A. Atomic Radius • Atomic radius is the average bonding radii between 2 nonbonding atoms

  14. Atomic Radius Trend

  15. B. Effective Nuclear Charge • Zeff is the “positive charge” felt by an electron.

  16. B. Effective Nuclear Charge

  17. VI. Ionic Radius • Radius of cations/anions • Effects physical and chemical properties of an ionic compound

  18. VI. Ionic Radius

  19. A. Ionization Energy • Minimum energy required to remove an electron from a gaseous atom

  20. B. Electron Affinity • Measure of how easily an atom will accept an electron

  21. C. Electronegativity • An atom’s ability to attract electrons to itself in a chemical bond.

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