S-Cool Revision Summary

S-Cool Revision Summary

The atom is made up of three sub-particles - the proton (+ve. and neutron (no charge. that are located in the nucleus of the atom and the electron (-ve charge. that is found orbiting the nucleus.

The nucleus has a positive charge.

The electrons are arranged in energy levels around the nucleus. Two electrons occupy the first, eight the second, eighteen the third.

Within the energy levels are sub-shells .

The region the electrons are said to occupy is called an orbital .

The four types of orbital are:

  1. s-orbitals - spherical can hold 2 electrons.
  2. p-orbitals - dumb-bell shaped, they go around in three's (px, py, pz. - so hold altogether a maximum of six electrons.
  3. d-orbitals are complicated in shape - they are grouped in five's hence can hold a maximum of 10 electrons.
  4. f-orbitals are complicated in shape - they are grouped in seven's - so altogether can hold 14 electrons.

The order that electrons fill is as follows:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p.

First ionisation energy:

The energy required to remove one mole of gaseous atoms to form one mole of gaseous ions.

The value of the first ionisation energy depends upon:

  1. The effective nuclear charge
  2. The distance between the electron and the nucleus
  3. The 'shielding' produced by lower energy levels.

Three types of chemical bonding:

  1. Ionic bonding: The transfer of electrons from metal atoms to a non-metal atom to form charged ions. The resulting product is held together by electrostatic attractions.
  2. Covalent bonding: atoms share one or more electrons to form a molecule. A single covalent bond is shared with each atom donating one electron.
  3. Co-ordinate or dative covalent bonding: a normal covalent bond, each atom donates one electron to the shared pair. In a co-ordinate bond electrons come from the same atom.

The shape of a molecule is decided by the valence shell electron pair repulsion theory: this states that molecules arrange their electron pairs to minimise repulsions between them.

Distorted shapes arise from the presence of lone pairs of electrons that cause greater repulsion than bonding pairs.