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Ch. 14 Periodic Trends Atomic Size – Quantum mechanical model doesn’t sharply define boundary to limit size – Atomic radius: ½ the distance between nuclei of 2 like atoms in a diatomic molecule • Atomic radius • Atomic size (cont.) Atomic Size Increasing Atomic Size (cont.) “Fatty Francium” Atomic Size Increasing Ionic Size Increase Cations Increase Anions Increase Atomic Size Ionic Size Trick to Remember Periodic Table of the Elements Fr “Fatty Francium” Atomic Size Ionic Size Ionization Energy – The energy required to remove an e- from a gaseous atom is called the ionization energy. – As you move from left to right across the periodic table the ionization energy increases b/c of the octet rule • Octet Rule: 8 e- in atom’s last energy level. (s2 + p6) - Noble Gases: highest ionization energies, don’t want to lose eLi doesn’t take much energy to lose eF want to gain an e- , therefore takes large amount of energy to pull off an e- Ionization Energy (cont.) Ionization Energy Increase Ionization Energy Increase Electronegativity • The electronegativity of an element is the tendency for the atoms to attract e- when they are chemically combined with another element • Noble Gases have NO electronegativity b/c they don’t gain e• Increase from left to right b/c of octet rule • Decrease when move down a group b/c of shielding effect Electronegativity (cont.) Electronegativity Increase Electronegativity Increase Summary of Trends “Friendly Fluorine” Periodic Table of the Elements Atomic Size Increasing Fr “Fatty Francium” Ionic Size Increasing F Electronegativity Increase Atomic Size Increasing Ionization Energy Increase Ionization Energy Increase Ionic Size Increasing Electronegativity Increase