CONTENT

• define periodicity: - patterns or trends across the periodic table which are repeated in other rows.
• describe and explain the trend of period 3 elements (atomic radius): DESCRIPTION atomic radius decreases across the period. [1 mark] EXPLANATION - nuclear pull increases (more protons). - outer electrons are more strongly attracted so are drawn in. - shielding is similar. [3 marks]
• define first ionisation energy: - amt of energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of unipositive ions.
• describe and explain the trend of first IE in period 3 elements: DESCRIPTION increases across period. EXPLANATION more protons and outer electrons are held more strongly so are more difficult to remove. except Mg to Al- outer electron is further away in p orbital and P to S where there is pairing in p orbital.
• describe and explain trend for EN: DESC increases EXP as nuclear pull increases outer electrons are held more strongly.
• describe and explain trend for melting point: DESC general decrease. EXP - Na to Al = increase (all metallically bonded increasing in strength) - Si forms macromolecular giant covalent structures so is exceptionally strongly bonded. - P to Cl depends on size of molecule and resulting VDW (P4 S8 Cl2). - Ar is the lowest since it is monatomic very low IM forces.
• describe and explain conductivity for period 3 elements:

  - general decrease

  - increase Na to Al- metallic bonds

  - more delocalised electrons

  - all other elements are covalently bonded so no delocalised electrons hence no conductivity.