Question

Amongst $N{O_3}^ - ,{\text{ }}As{O_3}^{3 - },{\text{ }}C{O_3}^{2 - },{\text{ }}Cl{O_3}^ - ,{\text{ }}S{O_3}^{2 - }\;and\;B{O_3}^{3 - }$​, the non-planar species are :

{A:N{O_3}^ - ,{\text{ }}C{O_3}^{2 - },{\text{ }}and{\text{ }}B{O_3}^{3 - }} \\\ {B:{\text{ }}S{O_3}^{2 - },{\text{ }}Cl{O_3}^ - ,{\text{ }}and{\text{ }}As{O_3}^{3 - }} \\\ {C:{\text{ }}C{O_2}^{3 - },{\text{ }}S{O_3}^{2 - }{,^{}}andB{O_3}^{3 - }} \\\ {D:{\text{ }}As{O_3}^{3 - },{\text{ }}C{O_3}^{2 - },{\text{ }}and{\text{ }}S{O_3}^{2 - }} \end{array}$$

Answer 1

A planar molecule refers to a molecule with all its atoms lying in one two-dimensional plane. Molecules having linear, square or triangular geometries are said to be planar molecules. In other cases, molecules may form three-dimensional shapes, like tetrahedrons, bipyramids or octahedrons.

Complete step by step answer:
First of all you have to find the hybridization of molecules. You can remember following rules to decide whether a molecule is planar or non-planar:

1. The molecule is not considered to be planar If there exists a $sp_3$ hybridized carbon (or nitrogen).
2. The molecule is considered to be planar if there is no $sp_3$hybridized carbon (or nitrogen), but there is one $sp_2$ h hybridized carbon or nitrogen atom.
3. The molecule is not considered to be planar if there is no sp3 hybridized atom but there are two $sp_2$ hybridized atoms which are separated by an even number of double bonds.
   We can say that the molecule is not planar if there exists either a $sp_3$ hybridized atom or two $sp_2$ hybridized atoms that are being separated by even numbers of double bonds. In other cases, its structure is planar. For the present scenario, consider the following table:

Species	Hybridization	Geometry	No. of lone pairs
NO3-	sp2		0
AsO33-	sp3		1
CO32-	sp2		0
ClO3-	sp3		1
SO32-	sp3		1
BO33-	sp2		0

$N{O_3}^ - ,{\text{ }}C{O_3}^{2 - } and {\text{ }}B{O_3}^{3 - }$ possess $sp_2$ hybridisation and thus, are planar species.

Hence, the correct answer is Option B.

Note:
You can remember that in order to find the hybridization of a molecule, count the valence electrons of each atom in a compound (fact to be noted is that count valence electron of hydrogen = 7). Add them all and divide the number by 8. Quotient represents bond pair while $\dfrac{{remainder}}{2}$ represents lone pair. Add quotient and $\dfrac{{remainder}}{2}$ and assume it as x. If (i) x is 3, molecule is planar with sp2 hybridisation, (ii) x is 2, molecule is linear with sp hybridization and x is 4, molecule is non-planar with sp3 hybridization.