From mg g 738 kj mg g emg 738 this is called

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Unformatted text preview: 8.13 76 77 Which is Bigger? • Cl or Cl- ? • K+ or K ? • Ca or Ca+2 ? • I- or Br- ? Ionization Energy Ionization Energy 78 IE = energy required to remove an electron IE from an atom (in the gas phase). from Mg (g) + 738 kJ ---> Mg+ (g) + eMg 738 This is called the FIRST This ionization energy because we removed only the OUTERMOST electron OUTERMOST Mg+ (g) + 1451 kJ ---> Mg2+ (g) + e1451 This is the SECOND IE. Trends in Ionization Energy Trends in Ionization Energy • IE increases across a IE period because the positive charge increases. positive • Metals lose electrons Metals more easily than nonmetals. nonmetals. • Nonmetals lose electrons Nonmetals with difficulty (they like to GAIN electrons). GAIN 79 80 Trends in Ionization Energy Trends in Ionization Energy • IE increases UP a IE group • Because size Because increases (Shielding Effect) (Shielding 81 Which has a higher 1st ionization energy? • Mg or Ca ? • Al or S ? • Cs or Ba ? 82 Electronegativity, χ Electronegativity, χ is a measure of the ability of an atom in a molecule to attract electrons to itself. itself. Concept proposed by Linus Pauling 1901-1994 Periodic Trends: Electronegativity • In a group: Atoms with fewer energy levels can attract electrons better (less shielding). So, electronegativity increases UP a group of elements. • In a period: More protons, while the energy levels are the same, means atoms can better attract electrons. So, electronegativity increases RIGHT in a period of elements. 83 84 Electronegativity 85 Which is more electronegative? • F or Cl ? • Na or K ? • Sn or I ? 86 The End !!!!!!!!!!!!!!!!!!!...
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