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Unformatted text preview: CHEM 1201 SI Worksheet Chapter 7 Periodic Trends of the Elements: Effective Nuclear Charge (Z eff ) : the charge felt by the valence electron(s) in an atom by the nucleus. The electron doesnt feel the complete effect of the positive nucleus b/c of the presence of core electrons o Shielding/Screening: the presence of core electrons that inhibit Z eff o Example: Atomic Size (explanation of trend): o going down P.T.: o going across P.T.: Ionic Size: Cl vs. Cl- Na vs Na + We can only compare radii of isoelectronic ions. Isoelectronic having the same total # of electrons. Examples N 3- O 2- F- Na + Mg 2+ Al 3+ # protons # electrons Ionization Energy: The energy required to remove an electron from an atom. The greater the Ionization Energy, the more difficult it is to remove an electron. Octet: Due to the fact that the most stable electron configurations are those of noble gases, main group atoms lose or gain electrons to form ions (cations, anions) whose electron configurations resemble those...
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