The oxygen is element number 8 of the periodic table. It is one of the highly reactive elements that readily forms compounds (especially oxides) with most elements. It is an oxidising agent, with a high electronegativity. After hydrogen and helium, it is the third most abundant chemical element. Oxygen is continuously reacting with living organisms. The proportion of oxygen in the atmosphere is 20.8%.
Index
OXYGEN ATOM
The atom of oxygen is composed of 8 protons and 8 electrons. It has 3 isotopeseach with 8, 9 or 10 neutrons. The main properties of the oxygen atom and its position in the periodic table are as follows:
ELECTRONS AND OXIDATION STATE ON THE OXYGEN ATOM
The oxygen atom has 8 electrons. According to the distribution of valence electronsthe first 2 electrons would be in the 1 shell, the next 6 electrons in the 2 shell (see electron distribution in atom). Eight electrons are needed to complete the second layer to make it stable. In order to complete this second layer with 8 electrons, oxygen tends to capture 2 electrons in its chemical bonds with other elements, hence its oxidation state is -2.
In the oxygen molecule, 2 atoms are bonded together through covalent bond with a double bond. Oxygen is the best oxidiser there is because the molecule is not very reactive (due to its double bond), and yet it is very electronegative, almost as electronegative as the fluorine.
Oxygen is one of the elements more electronegative of the periodic table, this means that it tends to trap electrons and form ionic bondsreacting with the rest of the elements, forming oxides, sulphates, nitrates, etc. In the Oxygen molecule, O2, 2 oxygen atoms are joined, through a covalent bond.
Oxygen is one of the most abundant elements on earth, present in the atmosphere and covering much of the human body (composed of water, H2O).
PHYSICAL-CHEMICAL PROPERTIES
| Name, symbol, number: | Oxygen, O, 8 | |
|---|---|---|
| Chemical series | Non-metals | |
| Group, period, block | 16, 2, p | |
| Atomic mass | 15,9994 u | |
| Electronic configuration | [He]2s22p4 | |
| Electrons per level | 2, 6 (image) | |
| Atomic properties | ||
| Electronegativity | 3,44 (Pauling scale) | |
| Atomic radius (calc) | 60 (48) pm (Bohr radius) | |
| Covalent radius | 73 pm | |
| van der Waals radius | 152 pm | |
| Oxidation State(s) | -2, -1 (neutral) | |
| Physical properties | ||
| Ordinary status | Gas (paramagnetic) | |
| Density | 1,429 kg/m3 | |
| Melting point | 50.35 K (-223 °C) | |
| Boiling point | 90,18 K (-183 °C) | |
| Enthalpy of vaporisation | 6.8061 kJ/mol | |
| Enthalpy of fusion | 0.4384 kJ/mol | |
| Molar volume | 17,36×10-3 m3/mol | |
| Various | ||
| Crystalline structure | cubic | |
| CAS NO | 7782-44-7 | |
| EINECS NO | 231-956-9 | |
| Specific heat | 920 J/(K-kg) | |
| Thermal conductivity | 0,026 74 W/(K-m) | |
USES OF OXYGEN
When defining the uses of oxygen, we distinguish between compounds formed with the oxygen atom and the uses of O2 as a molecule. Oxygen is one of the most abundant elements on earth, present in the atmosphere and covering a large part of the human body (composed of water, H2O).
USES OF MOLECULAR OXYGEN, O2
MEDICINE
O2 is the fundamental element that we take in when we breathe. In medicine, therefore, oxygen supplements are used. On many occasions, there are patients who need mechanical ventilation, usually at concentrations above the 21 % of the ambient air.
SPORTS AND TRAVEL SPACE
Modern space suits envelop the astronauts' bodies with pressurised air at low pressure. Scuba divers and mountain climbers sometimes use oxygen for sport. Those who travel in non-pressurised aircraft sometimes have a supplement of O2.
INDUSTRY
Most of the O2 produced for commercial purposes is used for the smelting of iron into steel, typically accounting for 55% of the commercially produced oxygen. A further 25 % of this oxygen is dedicated to the chemical industry.
OXYGEN-CONTAINING COMPOUNDS
OXIDES AND INORGANIC COMPOUNDS.
Water is the most common oxygen compound.
Due to the high electronegativity of oxygen, it forms chemical bonds with almost all elements to give the corresponding oxides. Oxides are also produced at room temperature, such as iron oxide (on rusted parts). The surface of metals such as aluminium and titanium oxidise in the presence of air and are covered with a thin oxide layer which passivates the metal and slows down corrosion.
Oxygen is also found in CO2 in the atmosphere. In the earth's crust as silicon oxides, ferric oxide, carbonates and silicates.
Water-soluble silicates with the forms Na4SiO4Na2SiO3 and Na2Yes2O5 are used as detergents and adhesives.
ORGANIC COMPOUNDS
Alcohols (R-OH), ethers (R-O-R), ketones (R-CO-R), aldehydes (R-CO-H), carboxylic acids (R-COOH), esters (R-COO-R), acid anhydrides (R-CO-O-CO-R) and amides (R-C(O)-NR).2) are organic compounds containing oxygen. There are many important O2-containing organic solvents, including: acetone, methanol, ethanol, isopropyl alcohol, furan, tetrahydrofuran, ethyl ether, dioxane, ethyl ethanoate, dimethylformamide, dimethyl sulfoxide, acetic acid, and formic acid.
It reacts spontaneously with many organic compounds at room temperature or below, in a process called autooxidation.