In nature there are three stable isotopes of oxygen: with atomic numbers 16, 17 and 18, but the first one prevails.As simple substances - diatomic gas O2 - Oxygen enters into the air and 21% of its volume.In a related form, this chemical element found in the composition of water, minerals and many organic substances.
Oxygen - this is the most abundant element on the planet.It takes 47.2% of the mass of the crust and is from 50 to 85% by weight of tissue of living organisms.
There are two allotropic modification of oxygen free - directly to the O2 and ozone O3.The latter concentrated in the upper atmosphere, forming the "ozone shield" that protects the Earth from harmful ultraviolet rays.
Atmospheric oxygen O2 - a colorle
ss, odorless gas is heavier than air.It has a density of 1.43 g / l and boils at -183oC.The liter of water under standard conditions is dissolved 0.04 g of oxygen, so it relates to sparingly soluble substances.
Industrially oxygen obtained by fractional distillation of liquid air: first distilled off therefrom nitrogen having a lower boiling point than that of oxygen in liquid form is substantially pure oxygen.Laboratory methods for producing oxygen is very extensive, but most often use: the decomposition of potassium chlorate KClO3, potassium permanganate, KMnO4, alkali metal nitrates (eg, NaNO3), hydrogen peroxide H2O2.The interaction with the alkali metal peroxides in carbon dioxide, as well as in the electrolysis of aqueous solutions of alkalis, acid salts of oxygenates as oxygen is liberated.In the latter case, the process comes to an electrical water decomposition: 2H2O = 2H2 + O2 ↑ ↑.
In reactions with other substances, oxygen acts as an oxidizer.Interacting with a simple substance, it forms oxide, but in the oxidation, for example, sodium and potassium are mainly formed peroxides (Na2O2 and K2O2).
O2 Reactions usually occur with the release of energy (exothermic), the only exception is endothermic reaction with nitrogen.For reactions with oxygen compounds called burning, produce heat and light.The oxidized oxygen (and, in particular, off) many inorganic and organic substances.
organic compound containing only carbon and hydrogen (possibly also oxygen) are burned to carbon dioxide and water.Nitrogen-containing substances during combustion form besides free nitrogen.