Moving across the period from left to right shows some important trends in the melting points of the oxides
This is a result of the change from metal to non-metal elements and differences in their structures
|
Oxide |
Tm/K |
Bonding |
Structure |
Comment |
|
Na2O |
1548 |
Ionic |
Ionic lattice |
Electrostatic attractions |
|
MgO |
3125 |
Ionic |
Ionic lattice |
Electrostatic attractions |
|
Al2O3 |
2345 |
Ionic-covalent |
Ionic-covalent lattice |
Some polarisation |
|
SiO2 |
1883 |
Covalent |
Macromolecular |
Strong covalent bonds |
|
P4O10 |
573 |
Covalent |
Molecular |
Weak intermolecular forces Dipole-dipole & van der Waals |
|
SO2 |
200 |
Covalent |
Molecular |
Weak intermolecular forces Dipole-dipole & van der Waals |
Aluminium oxide has some covalent bonding
Bonding is primarily ionic; the covalent characteristic is because it has a very small ion with a large positive charge and so it can approach closely to the oxygen ion and distort its electron cloud, giving an additional covalent bonding