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Effective Nuclear Charge (ENC)

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Effective Nuclear Charge (ENC) Effective Nuclear Charge is the pull felt on the valence electrons by the protons in the nucleus How tightly the valence electrons are ... – PowerPoint PPT presentation

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Title: Effective Nuclear Charge (ENC)


1
Effective Nuclear Charge (ENC)
  • Effective Nuclear Charge is the pull felt on the
    valence electrons by the protons in the nucleus
  • How tightly the valence electrons are pulled by
    the nucleus determines how the element will react
    in forming ions

2
Inner Shell Shielding
  • Inner shells (energy levels) of electrons
    shield or hide the valence electrons from the
    protons in the nucleus
  • Magnesium has 12 protons
  • Magnesium has 10 inner shell electrons
  • The valence electrons only feel the pull of 2
    protons

3
Determining ENC
  • ENC, in main group elements, is approximately
    equal to the number of valence electrons

4
Effects of Effective Nuclear Charge
  • On
  • Size
  • Ionization Energy
  • Electronegativity
  • Electron Affinity

5
Size
  • As ENC increases, the size decreases.
  • Therefore, the size decreases as you go across
    the periodic table
  • The size increases as you go down a family

6
Ionization Energy
  • This is the amount of energy needed to remove an
    electron making a positive ion.
  • Written as
  • A energy -gt A e-
  • As ENC increases, energy needed to remove an
    electron increases.
  • Energy to remove subsequent electrons also
    increases

7
Electron Affinity
  • This is the change in energy as an atom gains an
    electron making a negative ion.
  • Written as
  • A e- -gt A- energy
  • As ENC increases, Electron Affinity increases.

8
Electronegativity
  • The ability of an atom to attract electrons.
  • As ENC increases, Electronegativity increases.

9
Ion size
  • Positive (cat) ions get
  • Smaller
  • Negative (an) ions get
  • Larger
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