periodic 1 (period 3)

Question 1

describe the trend of melting point (type of bonding) across period 3

Answer 1

1. increases from Na to Al
   - metals have metallic bonding (charge density: q/r) with positive ions in a sea of delocalised electrons held in place by strong ESFOA
   - Na+ < Ca2+ < Al3+
   with increasing charge, greater charge density giving strong & more extensive metallic bonding
2. silicon has the highest MP among period 3
   - giant molecular structure with strong covalent bonds (atomic radius) that require a lot of energy to overcome
3. S8 > P4 > Cl2 > Ar
   - held by weak id-id that require little energy to overcome
   - more electrons give rise to a more polarisable e cloud and hence stronger id-id

Question 2

describe the trend in electrical conductivity across period 3

Answer 2

1. increases from Na to Al (Al the most)
   - increasing charge so more delocalised electrons
2. silicon
   - metalloid: semi-conductor (classified as a non conductor)
3. P to Ar
   - non metals, absence of mobile ions nor delocalised electrons

Question 3

describe trend of oxidation number of each element in their respective oxides and chlorides

Answer 3

increase positive integer

• oxygen & chlorine more EN
• period 3 have unoccupied, low-lying 3d orbitals which can be used for bonding through expansion of octet structure