Shapes of molecules

• What theory predicts the shape and bond angles of molecules?

  Valence shell electron pair repulsion theory (VSEPR)
• Why do electrons repel each other in a molecule?

  Because they are negatively charged
• How does the shape of a molecule minimize repulsive forces?

  By adopting a stable shape
• What are valence shell electrons?

  Electrons in the outer shell
• How do lone pair electrons differ from bonded pairs?

  Lone pairs repel more than bonded pairs
• How is repulsion treated between multiple and single bonds?

  It is treated the same as single bonds
• What is the order of electron pair repulsion?

  Lone pair-lone pair > lone pair-bond pair > bond pair-bond pair
• What shape does a molecule with 2 electron groups and 0 lone pairs adopt?

  Linear
• What is the bond angle for a trigonal planar molecule?

  120°
• What molecular geometry has 4 bonding groups and 0 lone pairs?

  Tetrahedral
• What is the bond angle for a tetrahedral molecule?

  109.5°
• What shape does a molecule with 3 bonding groups and 1 lone pair adopt?

  Trigonal pyramidal
• What is the bond angle for a trigonal pyramidal molecule?

  107°
• What shape does a molecule with 4 bonding groups and 2 lone pairs adopt?

  Bent
• What is the bond angle for a bent molecule with 4 bonding groups and 2 lone pairs?

  104.5°
• What molecular geometry has 5 bonding groups and 0 lone pairs?

  Trigonal bipyramidal
• What is the bond angle for a trigonal bipyramidal molecule?

  120° (equatorial), 90° (axial)
• What shape does a molecule with 5 bonding groups and 1 lone pair adopt?

  Seesaw
• What is the bond angle for a seesaw molecule?

  <120° (equatorial), <90° (axial)
• What shape does a molecule with 5 bonding groups and 2 lone pairs adopt?

  T-shaped
• What is the bond angle for a T-shaped molecule?

  <90°
• What shape does a molecule with 6 bonding groups and 0 lone pairs adopt?

  Octahedral
• What is the bond angle for an octahedral molecule?

  90°
• What shape does a molecule with 6 bonding groups and 1 lone pair adopt?

  Square pyramidal
• What is the bond angle for a square pyramidal molecule?

  <90°
• What shape does a molecule with 6 bonding groups and 2 lone pairs adopt?

  Square planar
• What is the bond angle for a square planar molecule?

  90°
• What is electronegativity?

  Power of an atom to attract electrons
• What happens to electron distribution in a covalent bond with different electronegativities?

  It becomes unsymmetrical
• What scale is used to assign electronegativity values?

  Pauling scale
• Which atom is the most electronegative on the Periodic Table?

  Fluorine
• How does nuclear charge affect electronegativity?

  Increased nuclear charge increases electronegativity
• What is atomic radius?

  Distance between nucleus and outer electrons
• How does atomic radius affect electronegativity?

  Increased atomic radius decreases electronegativity
• What is shielding in terms of atomic structure?

  Effect of filled energy levels on outer electrons
• How does shielding affect electronegativity?

  Increased shielding decreases electronegativity
• Which has higher electronegativity: sodium or caesium?

  Sodium
• What trend occurs in electronegativity down a group?

  It decreases down the group
• What trend occurs in electronegativity across a period?

  It increases across the period
• What happens to atomic radii across a period?

  They decrease across the period