All chemicals are composed of molecules, which are the smallest particles.They are electrically neutral and are composed of atoms, which are linked by covalent bonds.The ability of atoms of chemical elements to form molecules in a certain number of links are called valence.In connection with the emergence and development of the theory of chemical bonds this concept has undergone significant change and now has no clear scientific interpretation, mainly used in teaching purposes and is often identified with the degree of oxidation.If a molecule - is the smallest particle of matter, the atom is the smallest indivisible particle of a chemical element.Atom is also electrically neutral particle at its center is the nucleus consisting of positively charged protons, and around it is a cloud of electrons (negatively charged).So it is balanced the positive charge of the nucleus negatively charged electrons.To understand how to determine the degree of oxidation, and what it is necessary to consider the structure of molecules of specific substances.
The molecule of hydrogen chloride (HCl) between hydrogen and chlorine, there is one common pair of electrons.The hydrogen atom has one proton and one electron.The chlorine atom has 17 protons and 17 electrons, one of the seven electrons in the outer shell electron density has teamed up with an electron of the hydrogen atom, forming thus an electron pair: H: Cl.The molecule formed H2S 2 sulfur atom electron pair shared with the two hydrogen atoms: H: S: H. How to determine the degree of oxidation of the element, for example, chlorine and HCl in the molecule hydrogen and hydrogen sulfur in the molecule H2S?Valency gives an indication of an amount of bonds in the molecule formed or electron pairs, but does not show their displacement.
assumed that the electrons of atoms in a molecule are combined in the electron pairs which are shifted to the most elekrootritsatelnomu atom.Hydrogen and chlorine in the HCl can start a communication, which is shifted to a chlorine since it is the most electronegative.Thus, the hydrogen oxidation is plus 1, while chlorine - minus 1. Each hydrogen atom in the molecule H2S comes into contact with one sulfur atom, which in turn has two bonds.Both electron pairs in this case are shifted to a sulfur atom.Therefore, the oxidation of hydrogen plus equals 1, and the sulfur atom - negative 2. How to determine the degree of oxidation agent, e.g., HCl, H2S, O2, N2, Na, Ag, Si?The degree of oxidation of a simple or complex substance is always 0, as the substance composed of molecules or atoms and they are electrically neutral.Accordingly, the degree of oxidation of the element found in the molecule.
For example, with hypochlorous acid can consider how to determine the degree of oxidation of an atom Cl.HClO in the molecule, as in the molecule of any of the hydrogen is always (except hydrides) is characterized by the oxidation state plus 1, and the oxygen always - oxidation minus 2 (except barium peroxide and oxygen difluoride).Since the molecule itself has no charge, it is possible to write equation (1) + + x (- 2) = 0. This equation must be solved: x = 0 - (1) - (-2) = (1)Thus, it turns out that the degree of oxidation of Cl per molecule of hypochlorous acid plus equals 1. This example shows how to determine the degree of oxidation of any particular element in a molecule.First of all, the known values are arranged the elements, the valence or oxidation state which does not vary.
Thus, the degree of oxidation is called the notional value of the (formal charge of an atom in a molecule) used to write equations reactions associated with oxidation or reduction of various substances.This value is equal to the number of pairs of electrons, which is completely shifted towards the electronegative molecules of chemical elements.The degree of oxidation is recorded on the symbol of the atom.This entry indicates how to determine the degree of oxidation of a particular element in a molecule of any substance.For example, a record (Na + 1Cl-1) should be understood that in the molecule of salt oxidation sodium plus 1, minus 1, and chlorine, such as: (1) + (-1) = 0. In the molecule of potassium permanganate (K+ 1Mn + 7O-24) for potassium plus 1 to plus 7 of manganese, oxygen minus 2, that is: (1) + (7) +2 • (-2) = 0. In the molecule of nitric acid (H+ 1N + 5O-23) plus 1, for hydrogen, for nitrogen plus 5 for the oxygen minus 2, and the molecule is electrically neutral as a whole: (1) + (5) + 3 • (-2) = 0. In the molecule of nitrousacid (H + 1N + 3O-22), plus one for the hydrogen to nitrogen, plus 3, the oxygen minus 2, since the charge of the molecule is equal to zero, then: (1) + (3) + 2 • (-2) = 0. In the example of nitrogen shows that this atom may have a variety of different substances, oxidation of plus or minus 3 to 5 (with an interval of one unit).
