element oxygen is in the second period VI-th main group of old short version of the periodic table.Under the new standards, numbering - it is the 16th group.The corresponding decision was made by IUPAC in 1988.The formula of oxygen as a simple substance - O2.Consider its basic properties, role in nature and the economy.Let's start with the characteristics of the entire group of the periodic table, which is headed by oxygen.Element differs from related chalcogens and water is different from hydrogen the compounds of sulfur, selenium and tellurium.Cause all the hallmarks to be found, only to learn about the structure and properties of the atom.
chalcogen - related elements of oxygen
of similar properties of the atoms form a single group in the periodic system.Oxygen is headed chalcogen family, but differs from them in a number of properties.
atomic mass of oxygen - the founder of the group - is 16 a.e. m. chalcogen in the formation of compounds with hydrogen and metals exert their usual oxidation state of -2.For example, a composition of water (H2O), oxygen oxidation number equal to 2.
composition typical chalcogen hydrogen compounds has the general formula: N2R.By dissolving these substances form acids.Only hydrogen bonding oxygen - water - has special properties.According to the conclusions of scientists, it is an unusual substance is a very weak acid, and a very weak base.
sulfur, selenium and tellurium are typical positive oxidation state (4, 6) in compounds with oxygen and other non-metals having high electronegativity (EO).The composition of the oxides chalcogen reflect the general formula: RO2, RO3.The corresponding acids have a structure: H2RO3, H2RO4.
element corresponds to simple substances: oxygen, sulfur, selenium, tellurium and polonium.The first three members exhibit metallic properties.Formula oxygen - O2.Allotropic modification of the same element - ozone (O3).Both versions are gases.Sulfur and selenium - solid non-metals.Tellurium - metalloid substance, a conductor of electric current, polonium - metal.
Oxygen - the most abundant element
total content of atoms of an element in the earth's crust is about 47% (by weight).Oxygen is found in the free form, or as part of multiple compounds.Simple substance, whose formula of O2 stored in the composition of the atmosphere, constituting 21% air (by volume).Molecular oxygen is dissolved in water, it is between the soil particles.
We already know that there is another kind of existence of the same chemical element in the form of a simple substance.This ozone - gas produced at an altitude of about 30 km from the surface layer, often referred to as the ozone screen.Oxygen enters the water molecules in the many rocks and minerals, organic compounds.
structure of the atom of oxygen
Periodic table contains comprehensive information about oxygen:
- Number element - 8.
- charge of the nucleus - eight.
- total number of electrons - 8.
- E formula of oxygen - 1s22s22p4.
In nature there are three stable isotopes, which have the same serial number in the periodic table that is identical to the composition of protons and electrons but different numbers of neutrons.Isotopes are denoted by the same symbol - O. For comparison chart showing the composition of the three isotopes of oxygen:
properties of oxygen - a chemical element
On 2p sublevel of the atom has two unpaired electrons, which explains the emergence of powersoxidation -2 and +2.Two paired electrons can not disconnect to oxidation increased to 4, like sulfur and other chalcogen.The reason - lack of free sublayer.Therefore, the compounds of the chemical element does not exhibit oxygen valence and oxidation state equal to the group number in the short version of the periodic system (6).His usual oxidation number is -2.
Only with fluorine oxygen exhibits uncharacteristic positive oxidation state of +2.The value of EO two different strengths of non-metals: EA (D) = 3.5;EE (F) = 4. As a more electronegative element, fluoro strongly retained their valence electrons and pulls the particles onto the outer energy level of the oxygen atom.Therefore, in the reaction with fluorine it is oxygen reducing agent loses electrons.
Oxygen - a simple substance
English explorer D. Priestley in 1774 in the course of the experiments the gas emitted from the decomposition of mercuric oxide.Two years earlier, the same substance in its pure form was K. Scheele.Only a few years later the French chemist Antoine Lavoisier found that for the gas part of the air, and studied properties.The chemical formula for oxygen - O2.Was reflected in the composition of the recording material the electrons participating in the formation of a non-polar covalent bond - About :: About.Replace each binding electron pair of one feature: D = D.This formula oxygen demonstrates that the atoms in the molecule are linked by two common pairs of electrons.
Perform simple calculations and determine what is the relative molecular mass of oxygen: Mr (O2) = Ar (O) x 2 = 16 x 2 = 32. For comparison: Mr (Air.) = 29.The chemical formula different from formula oxygen ozone one oxygen atom.Hence, Mr (O3) = Ar (O) x 3 = 48. Ozone in oxygen is 1.5 times heavier.Physical properties
Oxygen - a gas without color, taste and smell (at standard temperature and pressure equal to atmospheric pressure).The substance is slightly heavier than air;It soluble in water, but in small quantities.Melting point oxygen is negative and is -218,3 ° C.The point at which the liquid oxygen is converted back into gas - is its boiling point.For molecules of O2 value of the physical quantity reaches -182,96 ° C.The liquid and solid oxygen gets a light blue color.
produce oxygen in the laboratory
When heated, oxygen-containing substances such as potassium permanganate, stands colorless gas that can be collected in a flask or test tube.If you bring in pure oxygen torch lit, it burns more brightly than in the air.Two other laboratory method for producing oxygen - decomposition of hydrogen peroxide and chlorate, potassium (potassium chlorate).Consider the circuit device, which is used for the thermal decomposition.
the tube or round-bottom flask is necessary to pour a little potassium chlorate, close the stopper with a gas outlet tube.It should be sent to the other end (the water) in the tilted flask upside down.The neck should be omitted in a glass or mold filled with water.When heated tubes, oxygen Berthollet salt.As he entered the vapor tube into the flask, displacing water from it.When the bulb is filled with gas, it is closed under the water stopper and inverted.Obtained in this laboratory experiment, oxygen may be used to study the chemical properties of the simple substance.
Burning
If incineration is carried out in the laboratory of substances in oxygen, it is necessary to know and comply with fire regulations.Hydrogen is combusted instantaneously in the air, mixed with oxygen in a ratio of 2: 1, it is explosive.Combustion substances in pure oxygen is much more intense than in the air.The reason for this phenomenon is the composition of the air.Oxygen in air is slightly larger portion of 1/5 (21%).Combustion - a reaction substances with oxygen, resulting in the formation of different products, primarily metal oxides, and nonmetals.Fire-hazardous mixture of O2 with flammable substances, in addition, the resulting compounds can be toxic.
Burning Candles usual (or matches), accompanied by the formation of carbon dioxide.The next experiment can be done at home.When burning the product under a glass jar or large glass, then stop burning once consumed all the oxygen.Nitrogen does not support combustion and respiration.Carbon dioxide - oxidation product - no longer reacts with oxygen.Clear lime water can detect the presence of carbon dioxide after burning candles.If the products of combustion pass through the calcium hydroxide, the solution becomes cloudy.A chemical reaction occurs between lime water and carbon dioxide, the resulting insoluble calcium carbonate.
oxygen production on an industrial scale
Cheapest process by which obtained free of air molecules O2, is not associated with a chemical reaction.In industry, for example, in the steel mills, the air is at a low temperature and high pressure liquefied.These essential components of the atmosphere such as nitrogen and oxygen boil at different temperatures.Separate air mixture with gradual warming to ambient temperature.Please stand nitrogen molecule, and then oxygen.The method of separation based on various physical properties of simple substances.Formula simple substance of oxygen is the same as it was before the cooling and liquefaction of air - O2.
As a result, some of the electrolysis reaction, too, oxygen, it is collected over the corresponding electrode.Gas industrial needs, construction companies in large volumes.Oxygen demand is constantly growing, especially needs it the chemical industry.Stored product gas for industrial and medical purposes in steel cylinders, equipped with a marking.An oxygen tank stained in blue or blue to distinguish it from other liquefied gas - nitrogen, methane, ammonia.
chemical calculations of formulas and equations reactions involving O2 molecules
numerical value of the molar mass of oxygen coincides with another value - relative molecular mass.Only in the first case, the present unit.Briefly formula substances oxygen and its molar mass is to be written as: M (O2) = 32 g / mol.Under normal circumstances, I beg any gas corresponds to the volume of 22.4 liters.Hence, 1 mol of O2 - is 22.4 liters substance 2 moles O2 - 44.8 liters.In the equation of the reaction between hydrogen and oxygen can be seen that the reaction of 2 moles of hydrogen and one mole of oxygen:
reactions involving one mole of hydrogen, the amount of oxygen of 0.5 mol • 22.4 l / mole = 112 liters.
role of O2 molecules in nature and human life
oxygen consumed by living organisms on Earth, and is involved in the circulation of substances in excess of 3 billion years.This is the main substance for respiration and metabolism, with the help of the decomposition of molecules of nutrients synthesized by the body needs energy.Oxygen is constantly consumed in the world, but its reserves are replenished through photosynthesis.Russian scientist K. Timiryazev believed that due to this process there is still life on our planet.
The role of oxygen in nature and economy:
- absorbed in the process of respiration by living organisms;
- involved in the reactions of photosynthesis in plants;
- included in the composition of organic molecules;
- processes of decay, fermentation, rust proceed with the assistance of oxygen, acting as an oxidant;
- used to produce valuable products of organic synthesis.
Liquid oxygen cylinders used for welding and cutting metals at high temperatures.These processes are carried out on the machine-building factories in the transport and construction companies.For work under water, underground, at high altitude in a vacuum also need people in the molecules of O2.Oxygen pillow used in medicine to enrich the composition of the air inhaled by people who are sick.Gas for medical purposes different from the almost complete lack of technical impurities, odor.
oxygen - the ideal oxidizer
known compounds of oxygen with all the chemical elements of the periodic table, except for the first members of the family of noble gases.Many substances immediately react with the O atoms, excluding halogens, gold and platinum.Of great importance are phenomena involving oxygen, which are accompanied by the release of light and heat.Such processes are widely used in the home and industry.In metallurgy, ore interaction with oxygen is called the firing.Pre-ground ore is mixed with oxygen-enriched air.At high temperatures the recovery of metals from sulfide to simple substances.The obtained iron and some non-ferrous metals.The presence of pure oxygen increases the speed of technological processes in various branches of chemistry, technology and metallurgy.
advent of cheap method for producing oxygen from air by separation into components at low temperatures stimulated the development of many areas of industrial production.Chemists believe O2 molecules and O atoms ideal oxidizing agents.These are natural materials, they are constantly renewed in nature, do not pollute the environment.In addition, chemical reactions involving oxygen often end with a synthesis of yet another natural and safe product - water.The role of O2 in the removal of toxic industrial waste water purification from impurities.In addition to oxygen, it is used for disinfection of allotropic modification - ozone.This simple substance possesses high oxidizing activity.When water ozonation decompose pollutants.Ozone is also detrimental effect on pathogenic microflora.
