Structure and Bonding

Intramolecular bonding
1. Ionic
  1. Metal atoms always LOSE electrons to form POSITIVE ions. Non-metal atoms always GAIN to form NEGATIVE ions.
  2. the attraction between positive and negative ions
  3. 3-D lattice structure
2. Metallic
  1. Electrostatic force of attraction between positive ions and delocalised electrons
  2. Occurs between two metals.
  3. good conductors of electricity = delocalised electrons
  4. greater number of electrons in outer electron shell = stronger metallic bond
3. Covalent
  1. electrostatic force of attraction between shared electrons and the positive nuclei
  2. Network
    1. strong covalent bonds
    2. high melting and boiling points
    3. Boron, Silicon, Carbon (in the form of DIAMOND and GRAPHITE)
  3. Molecular
    1. low melting and boiling points
    2. as the size of the molecule increases, melting point increases due to stronger intermolecular forces of attraction.
Intermolecular Forces (Van Der Waals)
1. London Dispersion Forces
  1. Uneven distribution of electrons, 'wobble' TEMPORARY DIPOLE
  2. Weakest
  3. short lived attraction between slight charge of one atom and slight charge of another
  4. ALL MOLECULES HAVE LDF'S, but can also contain other stronger forces
  5. the larger the dipole, the stronger the LDF
  6. small, but larger between bigger atoms
2. Dipole - Dipole Interactions
  1. Occur between polar molecules (PERMANENT)
  2. Asymmetrical molecules are polar, there is a permanent dipole
  3. in Symmetrical molecules, polarities cancelled out = non polar
  4. occur due to high difference in electronegativity (above 0.3)
3. Hydrogen Bonds
  1. Strongest
  2. exist between molecules that have a strong polar covalent bond
  3. only exist wen hydrogen is bonded to -NITROGEN -OXYGEN -FLUORINE
  4. very high melting and boiling points.
Bonding in Monatomic Elements
1. Noble gases have FULL outer electron shells.
2. they DO NOT need to combine with other atoms
3. occur as single atoms
4. there is weak attraction, as they can be solidified and liquefied.
5. the electrons 'wobble' and are unevenly distributed, creates temporary dipole, one side slightly negative, the other slightly positive.
  1. dipoles can induce other atoms to form dipoles, weak attractions between particles is therefore formed

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Structure and Bonding

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