1.4 Bonding

• What is an ionic bond?

  A bond between a positive and negative ion
• How are ions held together in an ionic bond?

  By strong electrostatic attraction
• What is the dot-and-cross diagram for NaCl?

  • Sodium loses one electron to form Na+
  • Chlorine gains one electron to form Cl-
• What is an ionic crystal?

  A giant lattice of ions
• How are ions arranged in an ionic crystal?

  Held together by electrostatic attraction
• Why do ionic compounds have high melting points?

  Strong electrostatic attraction requires much energy
• What is a covalent bond?

  A bond involving sharing of electron pairs
• What causes a covalent bond to form?

  Electrostatic attraction between nuclei and electrons
• What is a dative covalent bond?

  A bond where both electrons are donated by one atom
• Define electronegativity.

  The power to attract electron density in a bond
• What does bond polarity refer to?

  Separation of electric charge along a bond
• What is a temporary dipole?

  An uneven distribution of electrons creating charge
• What is a permanent dipole?

  A polar bond with different electronegativities
• What creates an induced dipole?

  Influence of a charged particle on electron distribution
• Compare bond character in covalent, intermediate, and ionic bonds.

  • Covalent bond: Electrons shared equally, no charge
  • Intermediate bond: Electrons shared unequally, partial charges
  • Ionic bond: Complete transfer of electrons, full charges
• What types of intermolecular forces exist?

  Temporary dipole, permanent dipole, hydrogen bonding
• How do temporary dipole interactions occur?

  Uneven electron distribution creates temporary dipoles
• What is a permanent dipole-dipole interaction?

  Attraction between oppositely charged permanent dipoles
• What are hydrogen bonds?

  Attraction between electron deficient hydrogens and electronegative atoms
• Why does water have a high melting and boiling point?

  Hydrogen bonds require much energy to break
• Why are alcohols soluble in water?

  Alcohols form hydrogen bonds with water molecules
• How does electron pair repulsion theory predict molecular shapes?

  • Shape determined by electron pair arrangement
  • Electron pairs repel, leading to specific shapes
  • Greater repulsion between lone pairs than bonding pairs
• What is the shape of BeCl2 and its bond angle?

  Linear, angle = 180°

  
• What is the shape of BCl3 and its bond angle?

  Trigonal planar, angle = 120°

  
• What is the shape of CH4 and its bond angle?

  Tetrahedral, angle = 109.5°

  
• What is the shape of NH3 and its bond angle?

  Trigonal pyramidal, angle = 107°

  
• What is the shape of NH4+ and its bond angle?

  Tetrahedral, angle = 109.5°

  
• What is the shape of H2O and its bond angle?

  Bent, angle = 104.5°
• What is the shape of SF6 and its bond angle?

  Octahedral, angle = 90°