You will need
- - handle;
- paper for records;
- - the periodic system of elements (periodic table).
The electrons in the atom occupy the available orbitals in the sequence, called the scale of energy:1s / 2s, 2p / 3s, 3p / 4s 3d 4p / 5s, 4d, 5p / 6s, 4d, 5d, 6p / 7s, 5f, 6d, 7p. On one orbital can accommodate two electrons with opposite spin rotation directions.
The structure of the electron shells Express through a graphical electronic formulas. To write formulas use the matrix. In one cell can accommodate one or two electrons with opposite spins. Electrons are represented by arrows. The matrix demonstrates that the s-orbital can accommodate two electrons, p orbitals 6, d – 10, f -14.
Consider the principle of making the electron-a graphic formula on the example of manganese. Find manganese in the periodic table. Its number 25 means 25 in the atom of electrons, is an element of the fourth period.
Record the serial number and the element symbol next to the matrix. In accordance with the scale of energy consistently fill in the 1s, 2s, 2p, 3s, 3p, 4s levels, typing for two electrons in a cell. Get 2+2+6+2+6+2=20 electrons. These levels are full.
You still have five electrons and unfilled 3d level. Place the electrons in the cells of a d-sublevel, starting from the left. Electrons with the same spin place in the cells of the first one. If all the cells are filled starting from the left, add the second electron with opposite spin. The five manganese d-electrons, are located one in each cell.
Electron-graphic formula clearly show the number of unpaired electrons that determine the valency.
Remember that chemistry is the science of exceptions. The atoms of auxiliary groups of the Periodic system there can be "leakage" of electrons. For example, chrome with serial number 24 is one of the electrons from the 4s-level moves into the cell d-level. A similar effect is, of molybdenum, niobium, etc. in addition, there is the concept of the excited state of the atom, when electrons are paired steamed and move on to the neighbouring orbitals. Therefore, in the preparation of electron-graphic formula of the elements of the fifth and subsequent periods secondary subgroups refer to the guide.
Advice 2 : How to arrange the degree of oxidation
Electrons are part of atoms. And complex substances, in turn, of these atoms (atoms form elements) and electrons are divided among themselves. The degree of oxidation shows how many electrons the atom itself took, how much and what is given. This figure can be determined.
You will need
- School textbook on chemistry 8-9, periodic table, table of electronegativity of elements (printed in school textbooks in chemistry).
First we need to indicate that the degree of oxidation - is a relative concept, the host for ion, that is, not deepening into the structure. If the item is in a free state, it is the simplest case formed by a simple substance, and therefore the degree of oxidation equal to zero. For example, hydrogen, oxygen, nitrogen, fluorine, etc.
In complex substances, things are different: electrons between atoms are not equally distributed, and the degree of oxidation helps to determine the amount given or accepted electrons. The degree of oxidation may be positive and negative. In the advantage of electrons is given, in the red accepted. Some elements of your degree of oxidation retain various compounds, but a this feature is no different. You need to remember an important rule - the sum of the degree of oxidation is always zero. The simplest example of gas: knowing that the degree of oxidation of oxygen in the vast majority of cases equal to -2 and using the above rule, we can calculate the degree of oxidation for carbon C. In the amount of -2 zero gives only +2, and hence the degree of oxidation of carbon +2. Let's complicate the task and we take for the calculations, the CO2 gas that the degree of oxidation of the oxygen remains -2, but the molecules of it, in this case two. Therefore, (-2) * 2 = (-4). The number in the sum gives zero -4, +4, that is, this gas, carbon has a degree of oxidation of +4. A more complex example: H2SO4 - hydrogen degree of oxidation of +1, oxygen -2. In particular compound 2 molecules of hydrogen and 4 of oxygen, i.e. the charges will be, respectively, +2 and -8. In order to sum to zero, you need to add 6 plus. Hence, the degree of oxidation of sulfur is +6.
When the connection is difficult to determine where plus, where a minus, necessary table of electronegativity (it is easy to find in the textbook in General chemistry). Metals often have a positive degree of oxidation, and the nonmetals negative. But for example, PI3 - both elements are nonmetals. The table shows that the electronegativity of iodine is 2.6, and phosphorus of 2.2. When compared, it turns out that the 2.6 is more than 2.2, that is, the electrons are pulled together in the direction of iodine (iodine has a negative degree of oxidation). Follow these simple examples, you can easily determine the degree of oxidation of any element in the compounds.
Not to be confused with metals and nonmetals, then the oxidation will be easier to find and not confusing.