In graphic (structural) formulas electronic couple forming communication between atoms is designated by a hyphen. Graphic formulas give an evident idea of an order of communications between atoms of substance and are especially widely used in organic chemistry. Hydrocarbons at an identical set of atoms can differ strongly in structure molecules. These distinctions well reflect structural formulas.
Instruction
1. Consider an order of drawing up a graphic formula on the example of phosphate magnesium. Its chemical formula – Mg3(PO4)2. At first draw a structural formula for orthophosphoric acid which formed this salt. For this purpose determine phosphorus valency in H3PO4. Hydrogen is a donor of electrons, it odnovalenten. Oxygen – an acceptor of electrons, its valency is equal to 2. Means, four molecules of oxygen attach eight electrons. Hydrogen, other five – phosphorus gives three of them. Therefore, phosphorus pyativalenten.
2. Write a phosphorus symbol. From it it is necessary to draw five hyphens designating electronic communications. Three of them take away groups – OH. There are two more hyphens and one atom of oxygen to which phosphorus also connects double communication.
3. Then make a graphic formula of phosphate of magnesium. In a salt molecule three atoms of metal are connected with two acid remains. Write down three symbols designating magnesium at line. Magnesium dvukhvalenten - about two hyphens communications have to depart from each symbol. In a salt molecule magnesium forces out hydrogen from acid and rises on its place. Each acid rest takes away three communications. To check itself, count amount of atoms in the turned-out structural formula. It has to coincide with number of atoms in a chemical formula.
4. In organic chemistry when writing graphic formulas it is accepted not to designate communication with hydrogen atoms. In the drawing examples of such structural formulas of organic compounds are shown.