An : 8
N : 8
Am : 15.9994 (3) g/mol
Group No : 16
Group Name : Chalcogen
Block : p-block
Period : 2
State : gas at 298 K
Colour : colourless as a gas, liquid is pale blue
Classification : Non-metallic
Boiling Point : 90.20K (-182.95oC)
Melting Point : 54.36K (-218.79oC)
Density : 1.429g/l
B. Discovery Information
Who : Joseph Priestley, Karl Wilhelm Scheele
When : 1774
Where : England/Sweden
C. Name Origin
Greek : oxus (acid) and gennan (generate). “Oxygen” in different languages.
Obtained primarily from by liquification and then fractional distillation of the air. World wide production is around 100 million tons.
Universe : 10000 ppm
Sun : 9000 ppm
Atmosphere : 2.095 x 105 ppm
Earth’s Crust : 4.74 x 105 ppm
Human : 6.1 x 108 ppb by weight; 2.4 x 108 ppb by atoms
Used in steel making, production of methanol (CH3OH), welding, water purification, cement and rocket propulsion. It is also required for supporting life and combustion. Oxygen is a major component of air, produced by plants during photosynthesis, and is necessary for aerobic respiration in animals.
Liquid and solid O2 are both a light blue colour. Ozone (O3) is a deeper blue colour. Oxygen is the second most common element on Earth, composing around 46% of the mass of Earth’s crust and 28% of the mass of Earth as a whole, and is the third most common element in the universe. Forms almost 21% of atmosphere.
Certain derivatives of oxygen, such as ozone (O3), singlet oxygen, hydrogen peroxide (H2O2), hydroxyl radicals and superoxide (O2-), are highly toxic. Highly concentrated sources of oxygen promote rapid combustion and therefore are fire and explosion hazards in the presence of fuels.
I. Allotropes of Oxygen
1. Dioxygen [ O2 ]
A gas at room temperature. Dioxygen exists as a diradical (contains two unpaired electrons) and is the only allotrope of any element with unpaired electrons.
2. Ozone [ O3 ]
Ozone was discovered by Christian Friedrich Schonbein in 1840, who named it after the Greek word for smell (ozein), from the peculiar odour in lightning storms. The actual odour from a lightning strike is from electron that have been freed during the rapid chemical changes that take place, and not ozone.
Ozone is a pale blue gas at standard temperature and pressure. It forms a dark blue liquid below -112oC and a dark blue solid below -193oC. Ozone is a powerful oxidizing agent. It is also unstable, decaying to ordinary oxygen (O2). It is present in low concentrations throughout the Earth’s atmosphere: ground level ozone is an air pollutant with harmful effects on lung function and in the upper atmosphere it prevents damaging ultraviolet light from reaching the Earth’s surface.
It is also formed from O2 by electrical discharges such as lightning, and by action of high energy electromagnetic radiation.
Some kinds of electrical equipment generate significant levels of ozone. This is especially true of devices using high voltages, such as television sets, laser printers, and photocopiers. Ozone is widely used in disenfecting water, killing bacteria and cleaning and bleaching fabrics.
3. Tetraoxygen [ O4 ]
The most recently discovered allotrope of oxygen. It is a deep red solid and is created by pressurizing O2 to the order of 20 GPa. Its properties are being studied for use in rocket fuels and similar applications, as it is a much more powerful oxidizer than either O2 or O3.
J. Reactions of Oxygen
Oxygen does not react with acids or bases under normal conditions.
1. Reactions with water
Oxygen will not react with water.
2. Reactions with air
Oxygen gas does not react with itself or nitrogen under normal conditions. However the effect of ultraviolet light upon oxygen gas is to form the blue gas ozone, O3.
3. Reactions with halogens
Irradiation of a low pressure mixture of oxygen and fluorine gases will produce dioxygen difluoride.
O2(g) + F2(g) –> F2O2(g)
K. Isotopes of Oxygen
16O [8 neutrons]
Stable with 8 neutrons
17O [9 neutrons]
Stable with 9 neutrons
18O [10 neutrons]
Stable with 10 neutrons