inorganic - periodicity 2.1

Question 1

the metal oxides

Answer 1

• sodium, magnesium and aluminium
• they form giant ionic lattices - where bonding extends throughout the compound
• this results in high melting points

Question 2

aluminium metal oxide

Answer 2

• ionic bond with covalent bond character
• aluminum forms a very small ion with a very large +3 charge
• it approaches O2- and distort the electron cloud

Question 3

how to predict ionic character of a bond

Answer 3

• considering the difference in electronegativity between two atoms
• the bigger the difference, the greater the ionic character of the bond

Question 4

the non metal oxides

Answer 4

• silicon, phosphorus and sulphur

Question 5

silicon oxide

Answer 5

• has a giant covalent (macromolecular) structure
• bonding extends throughout the whole giant structure
• high melting point due to the presence of many covalent bonds
• high energy needed to overcome those bonds

Question 6

phosphorus oxides

Answer 6

• exist as separate covalently bonded molecules
• solids
• intermolecular forces include weak van Der Waals and dipole-dipole forces
• melting point is relatively low - lower than silicon oxide

Question 7

sulphur dioxide and sulphur trioxide

Answer 7

• exist as separate covalently bonded molecules
• gases at 298K (room temp)
• low melting point - lower than silicon oxide and phosphorus oxides

Question 8

summary

Answer 8

• NaO2
  mp: 1548K
  bonding: ionic
  structure: giant ionic
• MgO
  mp: 3125K
  bonding: ionic
  structure: giant ionic
• Al2O3
  mp: 2345K
  bonding: ionic/covalent
  structure: giant ionic
• SiO2
  mp: 1883K
  bonding: covalent
  structure: macromolecular
• P4O10
  mp: 573K
  bonding: covalent
  structure: molecular
• SO3
  mp: 290K
  bonding: covalent
  structure: molecular
• SO2
  mp: 200K
  bonding: covalent
  structure: molecular