Covalency of central atom in Nitrate ion is ‘X’. Number of lone pairs in Nitrate ion is ‘Y’. Difference between X and Y is
4
1
2
3
Number of electron pairs(EP)=V+M-C+A2; V=Group number of central atom; M=-H, -X, -OH....monovalent groups attached to central atom ; C=Charge of cation ; A=Charge of anion...1 in NO3-, 1 in NO2-, 1 in ClO4-,1 in ClO3-,1 in ClO2-,1 in ClO-,2 in CO32- ; ....2 in SO32-, 2 in SO42-, 3 in PO43-, ; V=2,3.4,5,6,7,8 respectively for 2nd,13th,14th,15th, 16th, 17th, 18th group elements ; Number bond pairs, BP(according to VSEPR theory)=Number of atoms directly attached to central atom; =3 for NO3- ***According to VSEPR theory, double bond and triple bond are counted as one bond pair only ; If the bonded atom is Oxygen..... Magnitude of Oxidation state of central atom= Total bonds ; Number of atoms directly attached to central atom=sigma bonds ; Total bonds-sigma bonds = pi bonds ; Number lone pairs on central atom(LP)=EP-BP ; =0 in NO3- ; NO3--'3' bp +'0' lp on central atom ; sp2-Trigonal planar; ....Orientation of electron pairs....Trigonal planar; ....Total 8 lone pairs/ion ; Note; Each double bonded oxygen atom has '2' lone pairs on it ; Each single bonded oxygen atom with a negative charge has three lone pairs on it ; NO3- : Magnitude of Oxidation state of central atom= Total bonds=5 ; Number of atoms directly attached to central atom=sigma bonds=3 ; Total bonds-sigma bonds =1 pi bond.....'1' pπ-pπ bond, '1' dative bond ; Number of resonance structures=3 ; N-O bond order =Total bondsTotal resonance structures=43=1.33 ;
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