Periodicity

Question 1

Describe and explain the order of phosphorus, sulfur, chlorine and argon based on their melting/ boiling point

Answer 1

• S8 rings
  -> biggest of the three molecules
  -> strongest van der Waals forces
  -> highest boiling/melting point
• P4 tetrahedrons
• Chlorine diatomic
  -> smallest out of the first three
  -> weakest van der waals forces
  -> lowest mp/bp
• Argon
  -> exist as single atoms
  -> weakest van der waals forces of all non-metals
  -> lowest mp/ bp of all the period 3 elements

Question 2

Which oxides are basic/ acidic?

Answer 2

basic: (proton acceptors, usually metallic oxides)
* MgO₂
* MgO

acidic:
* SiO₂
* P₄O₁₀
* SO₂
* SO₃

amphoteric:
* Al₂O₃

Question 3

property of Al2O3 coating that causes Al to resist corrosion in water

Answer 3

insoluble / impermeable

Question 4

How to determine what molecule has the most covalent character?

Answer 4

1. Charge on the cation: Higher charge on the cation leads to more covalent character because the cation can polarize the anion more strongly.
2. Size of the cation: Smaller cations have stronger polarizing power, leading to more covalent character.
3. Size of the anion: Larger anions are more easily polarized, leading to more covalent character.