Oxygen is placed in the group VIA of the periodic table. All the elements of this group have ns2np4 outermost orbit electronic configuration.
Oxygen gas is prepared in the laboratory by heating potassium chlorate (KClO3) at about 420K in the presence of MnO2 as a catalyst in a hard glass test tube.
Oxygen gas can be prepared in the laboratory without application of heat from sodium peroxide (Na2O2). When acidified KMnO4 is dropped into sodium peroxide, oxygen is produced.
When coke or coal is burnt with limited supply of oxygen, carbon monoxide is formed. But with sufficient oxygen supply, carbon dioxide is produced.