Chem1201PReviewCh7 - Chemistry 1201 Review/Preview Chapter...

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Chemistry 1201 Review/Preview Chapter Seven Review Guide Dr. Saundra McGuire Spring 2007 Periodic Properties of the Elements I. Development of the Periodic Table A. Mendeleev’s Contribution When the properties of the elements were examined, Mendeleev discovered that  their chemical properties repeated in a regular way when they were arranged  according to increasing atomic weights.  The repeating behavior of the chemical  properties of the elements is called chemical periodicity or periodic behavior. B.   The Modern Periodic Table After more elements were discovered and their properties studied, it was clear that  the correct arrangement of the elements is in order of increasing  atomic   number , not  atomic weight.  The modern periodic table is arranged according to increasing  atomic number, and consists of vertical groups (or families) and horizontal periods.  (See pages 262-263 in the text.) II. Effective Nuclear Charge A. Effective Nuclear Charge - In multielectron atoms, the electron-to-electron repulsions reduce the strength of the nuclear charge felt by the electrons. The effective nuclear charge, Z eff , is the net nuclear charge actually felt by an electron, and is calculated as follows: Z eff = Z (the number of protons) – S (the electron shielding constant) B. Periodic Trends in Effective Nuclear Charge The effective nuclear charge, Z eff, increases as we move from left to right across the periodic table, but decrease as we move from top to bottom. (See pages 264-265.) III. Sizes of Atoms and Ions A. Atomic Radii generally decrease from left to right and increase from top to bottom. (Do Sample Exercise 7.2 without looking at the solution.) B. Ionic Radii depend on the type and size of the charge. Positive ions (cations)
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This note was uploaded on 03/23/2011 for the course CHE 1201 taught by Professor Staff during the Summer '09 term at UC Davis.

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Chem1201PReviewCh7 - Chemistry 1201 Review/Preview Chapter...

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