Length of a chemical bond is a distance of atomic nuclei in a molecule between centers. It is easily possible to understand that at formation of a chemical bond some mutual rapprochement or pulling of atoms to each other surely occurs therefore the distance between centers of their kernels will be less, than the sum of radiuses of separate atoms.
Instruction
1. Let's assume, there are two substances consisting of identical elements: And yes V. Prich distances between atoms of these two separate elements are known to you. How to calculate communication length in the molecule having the mixed structure AxBy? In some cases the rule of an arithmetic average works. If length of a chemical bond in the substance consisting of element A is equal, suppose, 140 pm (picometers), and in the substance consisting of element B – 190 pm, length of communication of AV will be (140 + 190)/2 = 165 pm.
2. For some substances it ruled fairly and yields very good results almost not different from those which are received experimentally. However there are also exceptions. For example, in a molecule of a bromovodorod of NVr by the rule of an arithmetic average length of a chemical bond has to be 151 pm, and in fact it is equal 141 pm.
3. It is possible to determine communication length, having resorted to various physical and chemical methods, for example elektronografiya. This method is based on the analysis of the diffraction picture which is formed at a deviation of a stream of electrons by molecules of the studied substance. Depending on that how strong was this deviation, the conclusion about length of a chemical bond in a molecule is drawn.
4. If the hybridization type in a molecule of polyatomic substance is known to you, you can determine communication length. It is known that in saturated hydrocarbons (alkanes) where each atom of carbon forms only unary communications with the next atoms of carbon and hydrogen, it has hybridization sp3-type, and length of communication is equal 1.54 pm. If any atom of carbon forms double communication, it has hybridization sp2-type, and length of a chemical bond then will be less – 1.34 pm. Well, and in that case if atom of carbon forms threefold communication (for example as in a molecule of acetylene, C2H2), length of a chemical bond will be even less – only 1.20 pm.