The number of the known chemical compounds is estimated in millions. In process of development of science and production they will become more and more, and all even the most qualified specialist is not able to remember them. But it is possible to learn to make formulas, and it will allow you to be guided much more confidently in the world of chemical compounds.
It is required to you
- - periodic table of D.I. Mendeleyev;
- - table of solubility of salts;
- - concept of valency.
Instruction
1. Consider the periodic table of chemical elements of D.I. Mendeleyev. You will see that all elements which are there are distributed on groups. Each of groups occupies a certain column. In the top line of the table you will see the Roman figures. They designate number of group and at the same time are an indicator of valency of the elements which are written down in each column.
2. Remember, what is valency. It is ability of atoms of this chemical element to give or accept electrons, connecting thus to atoms of other elements. Some elements mostly give electrons, others — accept. Depending on it they are carried to a class of oxidizers or reducers. Division it is in certain cases conditional. Some elements in different connections have different valency. By drawing up a formula consider that valency is more at that element which are in the table above and more to the right of another.
3. Define with what type of connection you should deal by drawing up a chemical formula. Connections can be binary. As a rule, they consist of two elements. Salts, acids and the bases belong to the second type. Remember what properties each of these groups has.
4. Make a formula of binary connection, based on the periodic table of D.I. Mendeleyev. Define what of the substances which are a part of connection is metal and what — nonmetal. According to the table look at the valency of each of these elements. The place of an element in a formula depends on it. Ahead it is accepted to write metal or an element which has a valency less. Write down consistently both elements. Look according to the table how many electrons each of them can give or accept.
5. Define how many communications have to be formed that the system turned out stable. For this purpose write down both elements nearby. Below put down the indexes designating quantity of electrons which each of elements can give or accept. Over indexes put down the signs "+" or "-", depending on whether the element is a donor or the recipient. Metal will have a sign "+", at oxygen, respectively, "-". Remove plus and minus and trade places indexes. In a general view the formula of simple binary connection can be expressed as the Ø1st E2u where E1 and E2 are elements with a different valency, and x and at — the amount of atoms of each element necessary for creation of a stable system.
6. Remove the general algorithm for creation of formulas of binary connections. It consists of four consecutive actions. You need to write down symbols of elements, to put down valency over each of them, to find the smallest multiple valencies and to divide the received result into the valency of each element. The final result will also be the index in a formula.
7. Look at the table of solubility of salts. Formulas of any difficult connections make of designations of conditional and real cations and anions. Elements which give electrons belong to the first group. They are located in the right column of the table. On the left side you can see anions, that is the accepting elements.
8. Write a number of designation of both elements or an element and group. Act just as by drawing up a formula of binary connection further. At first define how many electrons the element or group can give, then — how many it has to give that the stable system turned out.