Physical Properties and Reactions of Period 3 Oxides
PHYSICAL PROPERTIES OF THE PERIOD 3 OXIDES
These pages explain the relationship between the physical properties of the oxides of Period 3 elements (sodium to chlorine) and their structures. Argon is obviously omitted because it doesn't form an oxide.
A quick summary of the trends
The oxides
The oxides we'll be looking at are:
|Na2O |MgO |Al2O3 |SiO2 |P4O10 |SO3 |Cl2O7 |
| | | | |P4O6 |SO2 |Cl2O |
Those oxides in the top row are known as the highest oxides of the various elements. These are the oxides where the Period 3 elements are in their highest oxidation states. In these oxides, all the outer electrons in the Period 3 element are being involved in the bonding - from just the one with sodium, to all seven of chlorine's outer electrons.
The structures
The trend in structure is from the metallic oxides containing giant structures of ions on the left of the period via a giant covalent oxide (silicon dioxide) in the middle to molecular oxides on the right.
Melting and boiling points
The giant structures (the metal oxides and silicon dioxide) will have high melting and boiling points because a lot of energy is needed to break the strong bonds (ionic or covalent) operating in three dimensions.
The oxides of phosphorus, sulphur and chlorine consist of individual molecules - some small and simple; others polymeric.
The attractive forces between these molecules will be van der Waals dispersion and dipole-dipole interactions. These vary in size depending on the size, shape and polarity of the various molecules - but will always be much weaker than the ionic or covalent bonds you need to break in a giant structure.
These oxides tend to be gases, liquids or low melting point solids.
Electrical conductivity
None of these oxides has any free or mobile electrons. That means that none of them will conduct electricity when they are solid.
The ionic oxides can, however,
These pages explain the relationship between the physical properties of the oxides of Period 3 elements (sodium to chlorine) and their structures. Argon is obviously omitted because it doesn't form an oxide.
A quick summary of the trends
The oxides
The oxides we'll be looking at are:
|Na2O |MgO |Al2O3 |SiO2 |P4O10 |SO3 |Cl2O7 |
| | | | |P4O6 |SO2 |Cl2O |
Those oxides in the top row are known as the highest oxides of the various elements. These are the oxides where the Period 3 elements are in their highest oxidation states. In these oxides, all the outer electrons in the Period 3 element are being involved in the bonding - from just the one with sodium, to all seven of chlorine's outer electrons.
The structures
The trend in structure is from the metallic oxides containing giant structures of ions on the left of the period via a giant covalent oxide (silicon dioxide) in the middle to molecular oxides on the right.
Melting and boiling points
The giant structures (the metal oxides and silicon dioxide) will have high melting and boiling points because a lot of energy is needed to break the strong bonds (ionic or covalent) operating in three dimensions.
The oxides of phosphorus, sulphur and chlorine consist of individual molecules - some small and simple; others polymeric.
The attractive forces between these molecules will be van der Waals dispersion and dipole-dipole interactions. These vary in size depending on the size, shape and polarity of the various molecules - but will always be much weaker than the ionic or covalent bonds you need to break in a giant structure.
These oxides tend to be gases, liquids or low melting point solids.
Electrical conductivity
None of these oxides has any free or mobile electrons. That means that none of them will conduct electricity when they are solid.
The ionic oxides can, however,