Oxygen is a gas found in the atmosphere with a boiling point of -1830C.


Oxygen is found as 2 allotropes, O2 and O3, with the latter being called ozone. Ozone is much different than atmospheric oxygen, and its structure is the following:

Oxygen 1

Since the structure of O2 and O3 are different thees would then have different reactivities.

There are two places in which this reaction can take place:

Oxygen 2Oxygen 3

In the stratosphere where the ozone layer is present and it shields against UV light.

At sea level where it is considered a carcinogen and a pollutant.

Preparation of Oxygen

Oxygen can be prepared via a number of ways, some of which can be even prepared in a laboratory.

These include:

  • Reaction of peroxides with water.
  • Fractional distillation of air.
  • Heating oxides of metals which have a low reactivity.
  • Heating oxides of metals with a high oxidation state.
  • Reduction of hydrogen peroxide and chlorates both in the presence of MnO2.

Properties of Oxygen

Oxygen also has a number of properties:

  • Aireal oxidation
  • Combustion of hydrocarbons.
  • Burning metals in air.
  • Burning non-metal in air.


Metal oxides

There are 2 types of metal oxides:

Basic: MgO, CuO, CaO

Amphoteric: Al2O3, ZnO, PbO, SnO, SnO2

Covalent oxides

There are 2 types of covalent oxides:

Acidic: CO2, SO2, SO3, NO3, B2O3, P2O3, P2O5

Neutral: CO, NO, F2O

Normal oxides

A normal oxide is one in which the Oxygen either gains 2 electrons from a metal atom or shares 2 electrons with a non-metal.


In peroxide, Oxygen has a single bond to another Oxygen, forming an O22- ion.

Oxygen 4

Mixed oxide

A mixed oxide is one in which the metal has an equal ratio of 2 metal oxides, such as Fe2O3 and FeO mixture to give Fe3O4.

Hydrogen peroxide

Hydrogen peroxide is a liquid at room temperature due to extensive hydrogen bonding. It is prepared by the action of sulfuric acid on barium peroxide at 00C. Other peroxides can also be sued but the reaction would be too dangerous.

BaO2(S) + H2SO4 à BaSO4(s) + H2O2

Barium peroxide is added in excess in order to remove the 2 solids by filtration.

If the temperature is above 0oC the peroxide will start to decompose to form Oxygen

Hydrogen peroxide can act both as a reducing agent and as an oxidising agent:

Oxygen 5

Reducing agent:

H2O2 à O2

MnO42- à Mn2+

ClO à Cl

Oxidising agent:

H2O2 à H2O

Fe2+ à Fe3+

PbS à PbSO4  (black to white ppt.)