Question

How many of the following are non-polar planar molecules?
$B{F_{3}}$, $N{H_{3}}$, ${H_{2}}O$, $C{H_{4}}$, $C{Cl_{4}}$, $C{O_{2}}$, $Xe{F_{4}}$, $Xe{F_{2}}$, $S{F_{4}}$, $Xe{O_{3}}$

Answer 1

Hint: A planar molecule is a compound that possesses all of its atoms in the same plane. If an even number of lone pairs of electrons are present at the center of the atom, then they are considered polar molecules.

Complete step by step answer:
- As we already know, a molecule will be considered polar if there are different terminal atoms or lone pairs of electrons surrounding the central atoms otherwise it is nonpolar.
- To have a planar structure, a molecule should not possess $s{p_{3}}$ or $s{p_{2}}$ hybridized carbon or even nitrogen atoms. These atoms are separated by an even number of double bonds and no single bonds. Otherwise, the structure appears to be planar.

- $B{F_{3}}$: Boron is the central atom and fluorine is the terminal atom. Boron does not have any lone pair of electrons and all the electrons surrounding boron are connected to fluorine. Thus, it is a non-polar planar (trigonal) molecule.
 - $N{H_{3}}$: Since ammonia has three dipoles due to three bonds, they do not cancel out each other. Instead, form a net dipole moment making it a polar molecule.
- ${H_{2}}O$ : Due to the difference in electronegativities of hydrogen and oxygen, water molecules have a bent V shape. This makes the molecule a polar planar compound.
- $C{H_{4}}$: Methane has a tetrahedral shape leading to a symmetrical distribution of the molecule’s partial charges. Since no net charge is produced, it is nonpolar and not planar.
- $C{Cl_{4}}$: Carbon tetrachloride does not possess lone pairs on the central carbon atom. It has four bonds symmetrical to each other making it possible for dipole moments to cancel out easily. Thus, it has a non-polar planar structure.
- $C{O_{2}}$: Carbon dioxide has symmetry in bonding. Because the electronegativity difference between carbon and oxygen is 1, it is polar and has a linear planar structure.
- $Xe{F_{4}}$: Here are single bonds to each of the fluorine atoms and 2 lone pairs on the xenon atom. There is a large difference in their electronegativities. It is symmetrical in nature and thus no net dipole. So, it is a non-polar planar.
- $Xe{F_{2}}$: They have the same electronegativities, and similar electron pulling power. Due to their symmetrical nature, the dipole moment is canceled out, and thus it is a non-polar planar.
- $S{F_{4}}$: Sulphur has a lone pair of electrons as five of the electron pairs are bonded to fluorine. It has two bond angles. The lone pairs are at equatorial positions because it needs more space than the bonds. Thus, it is polar and not planar.
- $Xe{O_{3}}$: Xenon shows asymmetric charge distribution. It has a lone pair of electrons making the structure trigonal pyramidal. So, it is a polar planar molecule.

Note: A molecule or atom which does not have any charge present at the end due to the reason that electrons are equally distributed and those which symmetrically cancel out each other are the non-polar molecules.