Monitoring and Management > 4. The Atmosphere >
Compare the properties of the oxygen allotropes O2 and O3 and account for them on the basis of molecular structure and bonding
- Allotropy: The existence of two or more alternative forms of the same element in the same physical state.
- Two allotropes of oxygen are:
- Molecular oxygen (O2), also known as diatomic oxygen.
- Ozone (O3), also known as triatomic oxygen.
| Property | Molecular oxygen |
Ozone |
Explanation |
| Melting point | – 219°C | – 193°C | Ozone has a higher molecular mass than oxygen, and thus requires more energy in order to change state |
| Boiling point | – 183°C | – 111°C | (Same as for melting point, above) |
| Density | About the same as air | About 1.5 times that of air | Ozone is a larger molecule than oxygen |
| Solubility in water | Sparingly soluble | Considerably more soluble than oxygen | Ozone is slightly polar, while oxygen is non-polar |
| Stability | Very stable | Easily decomposed | It is much easier for ozone’s single coordinate covalent bond to be broken than oxygen’s double covalent bond |
| Oxidising strength | Moderately strong | Very strong | (Same as for stability, above) |
Properties of molecular oxygen and ozone
