(atoms, bonding and structure)

• Proton: 1+ charge, 1 amu mass

  Electron: 1- charge, 0.0005 amu mass

  Neutron: no charge, 1 amu mass
• Sub-atomic particles are protons, electrons and neutrons
• the further electrons are from the nucleus, the weaker the elctrostatic force. This means that electrons that are further have more energy and therefore move faster.
• Atomic number: bottom number, tells how many protons and electrons an atom has.
• Mass number: top number, tells the number of protons + neutrons (n=m-p)
• electric configuration shows the arrangement of electrons in shorthand or diagram
• electrons are as far apart as can be to prevent repulsion
• valence electrons are electrons in the outest shell
• Isotopes are atoms of the same element that have different number of neutrons
• Ar (relative atomic mass) = total mass of isotopes/100
• elements react because they want to acheive a full outer shell of electrons (like noble gases)
• metals will lose electrons in reaction and non-metals will gain electrons
• ions are atoms after they've gained or lost electrons
• vertical groups in the periodic table are equal to the number of valence electrons (e.g. group 3 has 3 valence electrons)
• Periods in the periodic table are equal to the number of shells an atom has (e.g. period 3 has 3 shells)
• ionic compounds have no charge
• 1. sum of charges on ion is 0
  2. more than one ion, use subscripts for number
  3. In formulae, metal first, then non-metal
  4. If more than one poly-atomic ion, use brackets with subscript outside
  5. non-metals end name with "ide"
  6. transition metals always form positive ion, roman numerals give charge
• reactivity depends on the number of electrons lost by a metal. The more electrons lost, the more reactive the metal. This is because a lot of energy is required to overcome the electrostatic force.
• Properties of ionic compounds:

  1. high melting point (strong electrostatic force needs lot of thermal energy in order to break)
  2. conducts electricity when melted/dissolved (mobile charged particles are attracted to electrodes)
  3. soluable in water (polar water molecules are attracted to charged ions whch supply energy to giant lattices)
• covalent bonding: sharing electrons between two or more atoms
• shared electrons attract positive nuclei of both atoms, this forms attraction between them called covalent bond
• Properties of covalent compounds:

  1. low melting point (weak intermolecular force does not requre much energy to break, it is liquid or gas at room temperature)
  2. not conductive (molecules are neutral, and since atoms acheive a full outer shell, there are no delocalised electrons)
  3. Insoluable in water (molecules are nonpolar therefore are not attracted to polar water molecules)
• the structure of a diamond has 4 carbon atoms joined to each atom by single covalent bonds. This is a tetrahedral structure, and has a giant network of covalent bonds.
• Diamond properties:

  1. melting point - very high (strong covalent bonds require much thermal energy to overcome)
  2. hardness - hardest substance known (structure is rigid, strong network of covalent bonds)
  3. electrical conductivity - not conductive (there are no delocalised electrons, all four valence electrons are bonded with atoms)
  4. uses - cutting tool, jewellery
• the structure of graphite has 3 single covalent bonds to each carbon atom. It's structure is made of hexagonal rings arranged into layers that slip and slide over each other. They are joined by intermolecular forces and a giant network of covalent bonds
• Graphite properties:

  1. melting point - relatively high (It's network of strong covalent bonds require high energy to overcome)
  2. hardness - soft (layers are held together by weak forces that can slip and slide over each other)
  3. electrical conductivity (free electrons are present between each layer, they can move freely allowing electricity to conduct)
  4. uses - lubricant, pencil lead
• the structure of Bucky balls (buckministerfullerene) has 3 single covalent bonds joined to each carbon atom. They are arranged into hexagonal and pentagonal rings that form a sphere shape
• Bucky balls properties:

  1. melting point - relatively low (weak intermolecular forces are easy to overcome with low termperatures)
  2. hardness - relatively soft (weak intermolecular forces are easily broken)
  3. electrical conductivity - conductive (there are delocalised electrons)
  4. uses - nano medicine, nano tubes