![]() ![]() The cation charge increases (size decreases) and on the right, the anion size increases, both variations leading to an increase in the covalency. The greater the positive charge, the smaller the cation becomes and the ionic potential is a measure of the charge to radius ratio. Large cations are to be found on the bottom left of the periodic table and small anions on the top right. Large charges: as the charge on an ion increases, the electrostatic attractions of the cation for the outer electrons of the anion increases, resulting in the degree of covalent bond formation increasing.This explains why for the common halides, iodides, are the most covalent in nature (I - 206 pm). Large anion: the high polarizability stems from the larger size where the outer electrons are more loosely held and can be more easily distorted by the cation.This explains why LiBr is more covalent than KBr (Li + 90 pm cf. Small cation: the high polarizing power stems from the greater concentration of positive charge on a small area. ![]() The polarizing power and polarizability that enhances the formation of covalent bonds is favoured by the following factors: The ability of a cation to distort an anion is known as its polarization power and the tendency of the anion to become polarized by the cation is known as its polarizability. If the degree of polarization is quite small, an ionic bond is formed, while if the degree of polarization is large, a covalent bond results. This results in a distortion, deformation or polarization of the anion. When two oppositely charged ions (X + and Y -) approach each other, the cation attracts electrons in the outermost shell of the anion but repels the positively charged nucleus. \)įajan's rules for predicting whether a bond is predominantly Covalent or Ionic CovalentĪlthough the bond in a compound like X +Y - may be considered to be 100% ionic, it will always have some degree of covalent character. ![]()
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