S2

• covalent bond


  strong electrostatic forces of attraction between a shared pair of elecrons and positively charged nuclei of the atom
• the greater the number of shared pairs of electrons the greater the attraction between the two covalently bonded atoms
• an incomplete octet are only in group...

  2 and 13
• electronegativity

  The tendency of an atom in a molecule to attract the shared pair of electrons towards itself
• bond polarity

  the distribution of electric charge across a chemical bond between two atoms
• covalent bond due to electrostatic attraction of nuclei to bond electrons
• intermolecular forces


  refer to the attractive forces between 2 or more molecules

  ex. hydrogen bonds, dipole-dipole forces
• intramolecular forces


  the attractive forces within a molecule or compound

  ex. the covalent bond, the ionic bond
• covalent network structure


  consist of a lattice of atoms all covalently bonded together to form essentially one giant molecule held together by very strong covalent bonds
• allotrope


  one or more forms of a chemical element that can exist in the same physical state
• polyatomic ions


  Ions made up of more than one atom, which have become charged due to the overall loss or gain of electrons
• Ionic bonding is the bonding that occurs when two oppositely charged ions experience an electrostatic attraction towards one another.
• The larger the lattice enthalpy the stronger the ionic bond
• properties of metals


  • Lustre (shiny appearance)
  • Sonority (sound when struck)
  • Malleability (can be reshaped on compression)
  • Ductility (can be drawn out into a wire)
  • Electrical conductivity
  • Thermal conductivity
• A metallic bond is a bond resulting from attractions between positive ions and surrounding mobile electrons
• The smaller the radius of the metal ion, the stronger the metallic bond. This is because of the shorter distance between the positive nucleus of the cation and the surrounding delocalised electrons.
• semi-conductor is a material that has an electrical conductivity value falling between that of a conductor
• isoelectronic ions


  atoms, ions or molecules that have some electronic structure and same number of valence electrons
• halogens


  group 17
• noble gas


  group 18
• amphoteric


  able to react both as a base and acid
• lattice


  a 3-dimensioned repeating structure made up of particles held by together by very strong interactions
• ionization energy


  the enthalpy change when an electron is removed from one mole of an atom in the gaseous state
• isolated atom


  noble gas
• lattice enthalpy

  the energy required to form one mole of an ionic compound from its ions in their gaseous state
• electron affinity


  the enthalpy change when an electron is added to an isolated atom in the gaseous state
• anions of elements on their own always end in -ide
• the greater the number of shared pairs of electrons the greater the attraction between the two covalently bonded atoms
• the non-bonding electrons exert more repulsion than bonding electron pairs
• Diamond


  each carbon atom is covalently bonded tetrahedrally to four other carbon atoms
• diamond has a rigid structure, with no plane of weakness. This makes it one of the hardest naturally occurring substances
• diamond is used as a cutting tool in drill tips
• in the diamond, all four elements in each carbon atom has been used for covalent bonding. it has no free electrons and not conduct electricity
• graphite


  each carbon atom is covalently bonded in a trigonal planar arrangement to three other carbon atoms to form hexagonal layers
• graphite


  the layers are held together by weak intermolecular forces of attraction between the layers which contain delocalised electrons
• graphite is a good lubricant and has a waxy feel as the layers can slide each other
• graphite is a good conductor of electricity as there are delocalised electrons that can move through the layers
• graphite is soft
• graphite has high melting and boiling point
• buckminsterfullerene


  each molecule of buckminsterfullerene consist of sixty carbon atoms, and it is not a true covalent network structure