3.1.1 - periodicity

• A period is the horizontal rows.

  a group is the vertical columns
• Periodicity is the repeating trends in chemical and physical properties
• First ionisation energy is the energy required to remove one electron from each atom in one mole of atoms in the gaseous state.
• Across period three more energy is needed to remove the first electron.
• First ionisation energy decreases between groups 2 to 3 because in group 3 the outer most electrons are in p orbitals and in group 2 they are in s orbitals. P orbitals have a higher energy, electrons are easier to remove as less energy is required.
• There is a decrease from groups 5 to 6 in ionisation energy because electrons in group 5 p orbital are single whereas group 6 are paired in the p orbital. There is more repulsion in group 6 orbitals so they are easier to remove.
• First ionisation energy decreases down a group because electron shielding increases - weaker attraction. Atomic radius increases - more shells, weaker attraction.
• successive ionisation energy is a measure of the amount of energy required to remove each electron in turn.
• Giant metallic lattices have:

  high melting and boiling points

  good electrical conductors

  malleability

  ductility
• Ductile metals are when the metal can be stretched and made into wires
• Malleability is when the metal can be shaped into different forms
• in period 2, lithium and beryllium are giant metallic structures; strong attraction between positive ions and delocalised electrons; metallic bonding.
• In period 3, sodium, magnesium and aluminium are giant metallic structures; there is a strong attraction between positive ions and delocalised electrons; there is metallic bonding
• In period 3, silicon is a giant covalent structure; with strong forces between atoms and have covalent bonds
• In period 3, P4, S8, Cl2 and Ar are simple molecular substances. They have Weak intermolecular forces between molecules and strong covalent bonds within molecules
• First ionisation energy decreases from one period to another because there is an increased atomic radius and an increase in electron sheilding.
• What is first ionisation energy?

  the energy required to remove one electron from each atom in one mole of atoms in the gaseous state