Electrons are a part of atoms. And complex substances, in turn, consist of these atoms (atoms form elements) and electrons among themselves divide. Oxidation level shows what atom how many electrons to itself took away and what how many gave. This indicator can be defined.
It is required to you
- The school textbook in chemistry 8-9 classes of any author, Mendeleyev's table, the table of electronegativity of elements (are published in school textbooks in chemistry).
Instruction
1. For a start it is necessary to designate that oxidation level is a concept conditional, taking communications for ionic, that is not going deep into the building. If the element is in a free state, then it is the simplest case - simple substance is formed, so its oxidation level is equal to zero. So for example, hydrogen, oxygen, nitrogen, fluorine, etc.
2. In complex substances everything is differently: electrons between atoms are distributed unevenly, and oxidation level helps to define quantity of the given or accepted electrons. Oxidation level can positive and negative. At plus the electrons are given, at minus are accepted. Some elements keep the oxidation level in various connections, but many do not differ in this feature. It is necessary to remember the important rule - the sum of oxidation levels is always equal to zero. The simplest example, SO gas: knowing that oxygen oxidation level is equal in the prevailing majority of cases-2 and using the above-designated rule, the sum can calculate oxidation level for S.V carbon about-2 zero gives only +2, so carbon +2 oxidation level. Let's complicate a task and we will take CO2 gas for calculations: oxygen oxidation level still remains-2, but its molecules in this case two. Therefore, (-2) * 2 = (-4). The number, in the sum with-4 giving zero, +4, that is in this gas carbon has oxidation level +4. The example is more difficult: H2SO4 - at hydrogen the oxidation level +1, at oxygen-2. In the taken connection 2 molecules of hydrogen and 4 oxygen, i.e. charges will be, respectively, +2 and-8. In order that in the sum to receive zero, it is necessary to add 6 pluses. Means, sulfur +6 oxidation level.
3. When in connection it is difficult to define where plus where minus, the table of electronegativity is necessary (it is simple to find it in the textbook in the general chemistry). Metals often have positive oxidation level, and nonmetals negative. But for example, PI3 - both elements nonmetals. In the table it is specified that electronegativity of iodine is equal 2.6, and phosphorus 2.2. When comparing it becomes clear that 2.6 it is more, than 2.2, that is electrons are pulled together towards iodine (iodine has negative oxidation level). Following the given simple examples, it is possible to determine easily the oxidation level of any element in connections.