EL 2

• Water molecules and ionic compounds

  Water molecules attract to charged ions, pulling the structure apart when dissolved
• Covalent bonds

  • Electrostatic attraction between shared electrons and the positive nucleus of the atoms
  • Can be single, double, or triple bonds based on the number of electrons being shared
• Dative covalent bond

  • One atom donating both electrons to form a bond, shown with an arrow
• Giant covalent structures

  • Graphite and diamonds
• Covalent bonding involves the sharing of outer electrons for atoms to obtain a full shell
• Dative covalent or coordinate bonds

  • One atom donates two electrons to another atom or ion to form a bond
  • Not as strong as traditional covalent bonds, useful for atoms like H+ that can't bond conventionally
• Ionic compounds

  • Form regular structures with giant repeating patterns
  • Dissolve in water due to attraction between polar water molecules and charged ions
  • Conduct electricity when molten or dissolved, not in solid form
  • Have high melting points due to strong electrostatic forces of attraction between oppositely charged ions
• Graphite structure

  • Layered structure where each carbon is bonded three times with the fourth electron being delocalized
• Carbon monoxide

  • Has a double covalent bond and a dative covalent bond
• Diamonds can be cut to make gemstones and are used in saw tips and drill bits for their durability
• Graphite has layers that slide over each other easily due to weak forces between them
• Diamonds

  • Each carbon atom is bonded four times in a tetrahedral shape, tightly packed rigid arrangement, high melting point, very hard, used in gemstones, poor conductor of electricity, insoluble
• Graphite has low density compared to current bond lengths
• Metallic bonding involves a giant metallic lattice structure with a sea of delocalized electrons surrounding positive metal ions
• Metals are malleable and ductile
• Metallic bonds have high melting points due to strong electrostatic attractions
• Graphite conducts electricity due to delocalized electrons between the layers
• Graphite

  • Has strong covalent bonds, high melting point, layers that slide over each other easily due to weak forces between them, used in pencils, conducts electricity due to delocalized electrons between layers, low density, insoluble
• Diamonds have a tightly packed rigid arrangement and high melting points
• Diamonds are poor conductors of electricity as they lack delocalized electrons
• Graphite is difficult to melt due to its many strong covalent bonds
• Metallic bonds have electrostatic attraction between the positive metal ions and the delocalized electrons
• Metals are good thermal and electrical conductors due to the mobility of delocalized electrons
• Impact of lone pairs on molecule shape

  Lone pairs repel bond pairs, reducing bond angles by two and a half degrees for each lone pair present
• Metallic bond

  • Insoluble in solid metals
  • Strong like covalent bonds, difficult to break
  • Malleable and ductile due to the ability of ion layers to slide over each other
• Malleable


  Can be bent into shape
• Reforming metals retains the structure due to the intact attraction between delocalized electrons and positive metal ions
• Methodology for determining molecule shape

  Draw dot cross structure, determine bond pairs and lone pairs, replace bond pairs with lone pairs if present, and calculate the total to determine the shape
• When hit with a hammer

  Metals can be bent into shape due to the retention of attractive force between delocalized electrons and positive metal ions
• Shapes of molecules

  • Molecules have specific shapes with specific angles due to bond pairs and lone pairs of electrons repelling each other equally
• Ductile

  Can be drawn into wires
• Shapes of molecules with no lone pairs

  1. Linear shape: Example - BCl2, Angle - 180 degrees

  2. Trigonal planar shape: Example - BF3, Angle - 120 degrees

  3. Tetrahedral shape: Example - CH4, Angle - 109.5 degrees

  4. Trigonal bipyramidal shape: Example - PCl5 Angle - 120 or 90 degrees

  5. Octahedral shape: Example - SF6 Angle - 90 degrees
• Shapes of molecules with lone pairs

  1. Pyramidal shape: Example - Ammonia, Angle - 107 degrees

  2. Bent shape: Example - Water, Angle - 104.5 degrees
• Effect of lone pairs on bond angles

  Lone pairs repel equally, maintaining the bond angle in trigonal planar shape
• Simple molecular substances are usually liquids or gases at room temperature and pressure
• Giant ionic substances have high melting and boiling points due to strong electrostatic forces between oppositely charged ions
• Simple molecular substances have low melting and boiling points due to weak intermolecular forces
• Nonpolar molecules, like hydrocarbons, do not dissolve in water and require nonpolar solvents
• Giant covalent substances conduct electricity only in the case of graphite
• Metallic substances have high melting points due to strong electrostatic forces between positive metal ions and delocalized electrons