Chemical Bonding — Chemistry STD 11 Science — Question
Maharashtra BoardEnglish MediumSTD 11 ScienceChemistryChemical Bonding4 Marks
Question
Explain electronic theory of valence.
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Answer
Electronic theory of valence:
Electronic theory of valence was proposed by Kossel and Lewis in $1916.$
They gave a logical explanation of valence which was based on the inertness of noble gases $($that is, octet rule developed by Lewis$).$
According to Lewis, the atom can be pictured in terms of a positively charged ‘kernel’ $($the nucleus plus inner electrons$)$ and outer shell that can accommodate a maximum of eight electrons. This octet of electrons represents a stable electronic arrangement.
Thus, according to this theory, during the formation of a chemical bond, each atom loses, gains or shares outer electrons so that it achieves stable octet.
The formation of $NaCl$ involves transfer of one electron from sodium $(Na)$ to chlorine $(Cl). Na^+ \ and \ Cl^–$ ions are formed which are held together by chemical bond. The formation of $H_2, F_2, Cl_2, HCl,$ etc., involves sharing of a pair of electrons between the atoms. In both the cases, each atom attains a stable outer octet of electrons.
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