Chemistry Chapter 6 Flashcards

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Questions and Answers

What are the three main factors of the repulsion theory?

  • The electron pairs around the central molecule determine its shape
  • The electron pairs around a central nucleus are trying to repel each other as much as possible
  • Different numbers of electrons result in different shapes
  • All of the above (correct)

What shape does 2 electron (bonding) pairs result in?

Linear / planar

What shape does 3 electron (bonding) pairs result in?

Trigonal planar

What shape does 4 electron (bonding) pairs result in?

<p>Tetrahedral</p> Signup and view all the answers

What shape does 5 electron (bonding) pairs result in?

<p>Triangular bipyramidal</p> Signup and view all the answers

What shape does 6 electron (bonding pairs) result in?

<p>Octahedral</p> Signup and view all the answers

What shape does two bonding pairs and two lone pairs result in?

<p>V-shaped / non-linear / bent</p> Signup and view all the answers

What shape does 3 bonding pairs and one lone pair result in?

<p>Tetrahedral</p> Signup and view all the answers

Why do lone pairs of electrons repel more than bonding pairs?

<p>They are slightly closer to the central atom and occupy more space than bonding pairs.</p> Signup and view all the answers

What is the shape of an ammonium ion?

<p>Tetrahedral</p> Signup and view all the answers

What is the shape of carbonate ions?

<p>Trigonal planar</p> Signup and view all the answers

What is the shape of sulfate ions (SO4 2-)?

<p>Tetrahedral</p> Signup and view all the answers

What is the shape of a nitrate ion?

<p>Trigonal planar</p> Signup and view all the answers

Why might a covalent bond experience a stronger attraction from one of the bonded atoms than another?

<p>Because one of the atoms may have more protons than the other.</p> Signup and view all the answers

What is electronegativity?

<p>The ability of an atom to attract the electrons in a covalent bond.</p> Signup and view all the answers

How is electronegativity measured?

<p>On the Pauling electronegativity scale.</p> Signup and view all the answers

Explain how hydrogen fluoride is electronegative.

<p>Fluorine is very electronegative and hydrogen is not, leading to a delta negative charge on fluorine and a delta positive charge on hydrogen.</p> Signup and view all the answers

What are the most electronegative atoms?

<p>Fluorine, chlorine, oxygen, and sulfur.</p> Signup and view all the answers

How can we explain the difference between different bonds?

<p>There is a spectrum of bond types ranging from pure covalent to polar covalent to pure ionic bonds.</p> Signup and view all the answers

What forms a pure covalent bond?

<p>When the two bonded atoms are the same or have a very similar electronegativity.</p> Signup and view all the answers

What forms a polar covalent bond?

<p>When the bonded atoms have a significant difference in electronegativity.</p> Signup and view all the answers

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Study Notes

Repulsion Theory

  • Electron pairs around a central atom dictate molecular shape.
  • Electron pairs repel each other to maximize distance.
  • The number of electron pairs influences the resulting shape.

Molecular Shapes Based on Electron Pairs

  • 2 Bonding Pairs:
    • Shape: Linear/Planar
    • Bond Angle: 180°
  • 3 Bonding Pairs:
    • Shape: Trigonal Planar
    • Bond Angle: 120°
  • 4 Bonding Pairs:
    • Shape: Tetrahedral
    • Bond Angle: 109.5°
  • 5 Bonding Pairs:
    • Shape: Triangular Bipyramidal
    • Bond Angles: 90° and 120°
  • 6 Bonding Pairs:
    • Shape: Octahedral
    • Bond Angle: 90°

Lone Pairs Effect on Molecular Shape

  • 2 Bonding Pairs & 2 Lone Pairs:
    • Shape: V-shaped/Non-linear/Bent
    • Bond Angle: 104.5° (due to lone pair repulsion)
  • 3 Bonding Pairs & 1 Lone Pair:
    • Shape: Tetrahedral
    • Bond Angle: 107°

Lone Pairs and Repulsion

  • Lone pairs repel more than bonding pairs due to closer proximity to the nucleus and greater spatial occupation.

Shapes of Ions

  • Ammonium Ion:
    • Shape: Tetrahedral
    • Bond Angle: 109.5°
  • Carbonate Ion:
    • Shape: Trigonal Planar
    • Bond Angle: 120°
    • Features: One double-bonded oxygen to carbon.
  • Sulfate Ion (SO4 2-):
    • Shape: Tetrahedral
    • Bond Angle: 109.5°
    • Structure: 2 double-bonded and 2 single-bonded oxygens.
  • Nitrate Ion:
    • Shape: Trigonal Planar
    • Involves a dative covalent bond with one oxygen (-2 charge), a single covalent bond (-1 charge), and a double covalent bond (no charge).

Electronegativity

  • Defined as the ability of an atom to attract electrons in a covalent bond.
  • Measured on the Pauling scale, which ranges from 0.4 to 4.0.
  • Most Electronegative Elements:
    • Fluorine (4.0), followed by chlorine, oxygen, and sulfur.

Bonding Differences

  • Bonds vary in types based on electronegativity differences:
    • Pure Covalent: Electronegativity difference = 0
    • Polar Covalent: Difference between 0 and 1.8
    • Pure Ionic: Difference greater than 1.8
  • Pure Covalent Bond: Formed between identical or similar electronegativities, resulting in non-polar bonds.
  • Polar Covalent Bond: Formed when there is a significant electronegativity difference, causing unequal electron sharing.

Example of Electronegativity in Molecules

  • In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen, resulting in a partial negative charge on fluorine and a partial positive charge on hydrogen.

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