To draw the resonating structure of NO2
No. of valence electrons for N = 5
No. of valence electrons for O = 2 × 6 = 12
Total no. of valence electrons = 5 + 12 = 17
The N and O atoms are arranged in such a way that the less electronegative atom N is placed as the central atom.
Electron pairs are placed between bonds and distributed around the atoms to form octet as shown. Both the O atoms have their complete octet but N has only 5 electrons.
A pair of electrons is transferred from O to the bond between O and N. Both the O atoms have their complete octets and N has 7 electrons.
The resonating structures of NO2 can be shown as:
To draw the resonating structure of N2O5
No. of valence electrons for N = 2 × 5 = 10
No. of valence electrons for O = 5× 6 = 30
Total no. of valence electrons = 10 + 30 = 40
Just like in NO2, the valence electrons are distributed between bonds and then around atoms to complete their octet.
(Formal charge of each atom is enclosed in bracket)
When the valence electrons around the atoms, the formal charge of N atoms are found to be +1 while that of the center O is +2. But N is less electronegative than O. So, the electrons can be re-arranged as
The centre O now has formal charge 0 and the terminal O atoms have formal charge -1 which the N atoms have +1 which is more appropriate since O is more electronegative than O.
The resonance structures of N2O5 can be shown as:
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