Periodic Trends

Periodic Trends

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  November 18 th & 19 th , 2009 Periodic Trends
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  Periodic Law Whenelements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals (periodically).
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  Periodic Properties AtomicRadius Size of atom First Ionization Energy Energy required to remove one e - from a neutral atom. Electronegativity How much an atom pulls Electrons towards itself in a bond © 1998 LOGAL © 1998 LOGAL
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  Atomic Radius Sizeof atom Li Ar Ne K Na
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  Atomic Radius Increasesto the LEFT and DOWN Francium is the largest atom
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  Atomic Radius Whylarger going down? Higher energy levels have larger orbitals Why smaller to the right? Shielding – core electrons block the attraction between the nucleus and the valence electrons Increased nuclear charge without additional shielding pulls electrons in tighter
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  Ionization Energy Energyrequired to remove an electron It ALWAYS requires some energy to remove an electron!! K Na Li Ar Ne He
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  Ionization Energy IncreasesUP and to the RIGHT Helium has the highest Ionization Energy
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  Ionization Energy Whyopposite of atomic radius? In small atoms, e - are close to the nucleus where the attraction is stronger and they are harder to pull off Small atom = high ionization energy In larger atoms, the valence electrons are easier to pull off Large atom = low ionization energy
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  Electronegativity Ability ofan atom to pull electrons towards itself in a bond.
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  Increases UP andto the RIGHT Fluorine has the highest electronegativity Noble gases have no electronegativity because they don’t form bonds Electronegativity
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  Electronegativity Why oppositeof atomic radius? In small atoms, there is less shielding so the protons pull harder on electrons Small atom = high electronegativity In larger atoms, there is more shielding Large atom = low electronegativity
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  Examples Which atomhas the larger radius? Be or Ba Ca or Br Ba Ca
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  Examples Which atomhas the higher Ionization Energy? N or Bi Ba or Ne N Ne
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  Examples Which atomhas the higher electronegativity? Li or C Cr or Kr C Kr?