Electro-negativity

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Electro-negativity
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Ionic covalent continuum

• When chlorine and hydrogen react the covalently
  bonded HCL is made
• When chlorine and sodium react ionicly bonded
  NaCl is formed
• Why does Cl share electrons with H yet remove
  electrons from Na?

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Why does Cl share electrons with H yet remove
electrons from Na?

• Hydrogen holds its electrons really tightly in
  H-H gas
• Sodium is a metal the doesnt hold its valance
  electrons as tightly
• Chemists use the term electronegativity

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Electronegativity
What is it?

• Electronegativity is the power of an atom to
  attract electron density

in a covalent bond
Remember the above definition
Or in layman's terms the attractiveness of an
atom to electrons in a bond
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Electronegativity
Paulings electronegativity scale

• The higher the value, the more electronegative
  the element

• Fluorine is the most electronegative element

• It has an electronegativity value of 4.0

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Electronegativity
Paulings electronegativity scale
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Electronegativity
Paulings electronegativity scale

F

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Electronegativity
Paulings electronegativity scale

F 4.0

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Electronegativity
Paulings electronegativity scale

Li 1.0 F 4.0

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Electronegativity
Paulings electronegativity scale

Li 1.0 Be 1.5 F 4.0

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Electronegativity
Paulings electronegativity scale

Li 1.0 Be 1.5 B 2.0 F 4.0

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Electronegativity
Paulings electronegativity scale

Li 1.0 Be 1.5 B 2.0 C 2.5 F 4.0

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Electronegativity
Paulings electronegativity scale

Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 F 4.0

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Electronegativity
Paulings electronegativity scale

Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0

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Electronegativity
Paulings electronegativity scale

Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0
Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0
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Electronegativity
Paulings electronegativity scale
H He
Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Ne
Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 Ar
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Electronegativity
Paulings electronegativity scale
H 2.1 He
Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Ne
Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 Ar
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Electronegativity
Paulings electronegativity scale
H 2.1 He -
Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Ne -
Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 Ar -
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So what does all this mean?

• Same atoms bonding same electronegativity
  pure covalent bond
• Different atoms bonding different
  electronegativity Polar covalent or Ionic
  bond
• Confused? How do we tell which one?
• Difference in electronegativity Covalent and
  ionic are a opposite ends of the same scale

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Ionic Bond
Polar Covalent
Covalent
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If the difference in electronegativities is
between

• 1.7 to 4.0 Ionic Bond
• 0.3 to 1.7 Polar Covalent
• 0.0 to 0.3 Non-Polar Covalent