bonds

• Chemical bond


  Mutual attraction between two atoms resulting from the simultaneous attraction between their nuclei and the outer electrons
• The energy of the combined atoms is lower than that of the individual atoms resulting in higher stability
• Lewis dot diagram


  Structural formula in which valence electrons are represented by dots or crosses
• Valence electrons


  Electrons in the highest energy level of an atom in which there are electrons
• Covalent bond


  Sharing of electrons between two atoms to form a molecule
• Molecule


  Group of two or more atoms covalently bonded and that function as a unit
• Bonding pair


  Pair of electrons that is shared between two atoms in a covalent bond
• Lone pair


  Pair of electrons in the valence shell of an atom that is not shared with another atom
• Electronegativity


  Measure of the tendency of an atom in a molecule to attract bonding electrons
• Non-polar covalent bond


  Bond in which the electron density is shared equally between the two atoms
• Polar covalent bond


  Bond in which the electron density is shared unequally between the two atoms
• Bond energy

  Energy needed to break one mole of its molecules into separate atoms
• Bond length


  Average distance between the nuclei of two bonded atoms
• Bond energy and bond length

  Bonds with a shorter bond length require more energy to break than bonds with a longer bond length
• Strength of a chemical bond


  Shorter bond length,

  smaller bonded atoms,

  more bonds (single, double, triple) between the atoms result in stronger bonds
• Intermolecular forces

  Forces between molecules
• 6 Types of intermolecular forces

  • Mutually induced dipole forces or London forces
  • Ion-induced dipole forces
  • Dipole-dipole forces
  • Dipole-induced dipole forces
  • Hydrogen bonding
  • ion-dipole
• Intermolecular forces are different from interatomic forces (intramolecular forces)
• 
  

  Strength of induced dipole forces increases with molecular size for non-polar molecules
• Intermolecular forces

  Affect boiling point, melting point, vapour pressure and solubility
• Boiling point: The temperature at which the vapour pressure of a substance equals atmospheric pressure. The stronger the intermolecular forces, the higher the boiling point
• Melting point: The temperature at which the solid and liquid phases of a substance are at equilibrium. The stronger the intermolecular forces, the higher the melting point
• Vapour pressure: The pressure exerted by a vapour at equilibrium with its liquid in a closed system. The stronger the intermolecular forces, the lower the vapour pressure
• Solubility: The property of a solid, liquid, or gaseous chemical substance (solute) to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution
• Non-polar covalent bond


  Atoms attract the shared pair(s) of electrons equally
• Polar covalent bond


  One atom attracts the shared pair(s) of electrons more than the other atom
• Non-polar molecule


  Has an even distribution of charge and is symmetrical
• Polar molecule


  Has an uneven distribution of charge and is non-symmetrical
• Linear molecules consisting of identical atoms have a pure covalent, non-polar bond
• Linear molecules consisting of different atoms have a polar covalent bond due to unequal sharing of electrons
• Hydrogen bonds


  H in compound with FON
• Intermolecular forces


  • The higher the intermolecular forces, the more energy is required to break the bonds
• Hydrogen bonds are stronger than dipole-dipole forces
• ICE


  1.Intermolecular forces

  2.compare strength

  3. Energy
• trigonal planar

  • 4 atoms bonded to central atom and no lone pairs
• Hydrogen bonds


  A specific type of a dipole-dipole force and therefore also a Van der Waals force
• Types of particles and associated forces

  • Ions - Coulombic forces/electrostatic forces
  • Ion and polar molecule - Ion-dipole
  • Two polar molecules - dipole-dipole
  • Ion and non-polar molecule - ion induced dipole and non-polar molecule - Dipole-dipole
  • Non-polar molecules - Ion-induced dipole, Dipole-induced dipole (or hydrogen bond in special cases), Dispersion (London) forces/induced dipole forces
• 5 influences of intermolecular force

  • state of matter
  • size of molecule
  • density
  • boiling and melting points
  • viscosity
• As the boiling point of a liquid increases, the energy required to overcome the intermolecular forces increases.
• The greater the density of a substance, the closer together the particles are and hence the stronger the intermolecular forces between them.