state and explain fajan's rule to explain the geometry of covalent molecules.
Answers
Answer:
Explanation:
While it is taught that the chemical bonds are divided broadly into ionic and covalent types, however, in reality, most of the bonds are neither purely ionic nor purely covalent. These terms are used to indicate two extreme cases. The ionic bond refers to complete transfer of electrons from one atom to the other, whereas the pure covalent bond involves equal sharing of electrons. Nevertheless, the nature of chemical bonds in most of the compounds are somewhere in between above said two extremes.
In general, it is expected that the ionic compounds are soluble in polar solvents like water and show high melting and boiling points as well as exhibit electrical conductivity in the liquid state. As a rule, these compounds should be sparingly soluble in non polar solvents like benzene, carbon tetrachloride etc. However, it is observed that few of the ionic compounds are also fairly soluble in them and also exhibit somewhat less than anticipated melting points and electrical conductivity in the molten state .
It is also observed that some of the covalent compounds are soluble in water and exhibit electrical conductivity, though not very much, in the molten state.
This clearly shows more or less covalent nature is also possible for the ionic compounds and vice versa. These observations can be explained by the concept of polarization and thus led to the formulation of Fajan's rules which help in deciding the nature of chemical bonds.
Polarization
Fajan's rules
POLARIZATION
The negative charge on an isolated anion is evenly distributed around the nucleus. But in presence of a cation, the electron density is distorted towards it. Thus the negative charge is unevenly distributed over the anion. One end of the anion gets relatively more negative charge than the other end. This condition is referred to as polarization.