Question

In which molecule, all atoms are coplanar?
A.\[{\text{C}}{{\text{H}}_{\text{4}}}\]
B. \[{\text{B}}{{\text{F}}_{\text{3}}}\]
C.\[{\text{P}}{{\text{F}}_{\text{3}}}\]
D.\[{\text{N}}{{\text{H}}_{\text{3}}}\]

Answer 1

Hint: To answer this question,recall the formula to calculate the hybridization of a molecule. The value of the hybridisation number will help determine the shape which is dependent on the hybridization number.
Formula used:
 For neutral molecules: ${\text{Hybridisation = lone pair + bond pair}}$

Complete step by step answer:
The important thing to remember is that the molecules exhibiting \[s{p^2}\]hybridisation are planar. This is because hybridisation leads to triangular planar shape. \[s{p^2}\]is observed when one s and two p orbitals of the same shell of an atom mix to form 3 equivalent orbitals.
First, determine the hybridization of the given molecules and then determine the shape and geometry of the molecules:
\[{\text{C}}{{\text{H}}_{\text{4}}}\]​−The central atom forms 4 bonds and has 0 lone pair. The hybridisation is \[s{p^3}\] with tetrahedral geometry. This shape is non-planar, the option is incorrect and is eliminated.
\[{\text{B}}{{\text{F}}_{\text{3}}}\] − The central atom forms 3 bonds and has 0 lone pair. The hybridisation is \[s{p^2}\] with trigonal planar geometry. This shape is planar, the option is correct.
\[{\text{P}}{{\text{F}}_{\text{3}}}\]- The central atom forms 3 bonds and has 1 lone pair. The hybridisation is \[s{p^3}\] with trigonal pyramidal geometry. This shape is non-planar, the option is incorrect and is eliminated
\[{\text{N}}{{\text{H}}_{\text{3}}}\] − The central atom forms 3 bonds and has 1 lone pair. The hybridisation is \[s{p^3}\] with trigonal pyramidal geometry. This shape is non-planar, the option is incorrect and is eliminated.
So, \[{\text{B}}{{\text{F}}_{\text{3}}}\] the molecule is coplanar and is the correct answer.

Hence, the correct option is B.

Note:
Even if you are not able to calculate the hybridisation using the above-mentioned you can find the hybridization $(X)$ using the formula: \[\frac{1}{2}({\text{V}} + {\text{H}} - {\text{C}} + {\text{A}})\] where
${\text{V}}$= Number of valence electrons in the central atom
${\text{H}}$= Number of surrounding monovalent atoms
${\text{C}}$= Cationic charge
${\text{A}}$= Anionic charge. The value of X will determine the hybridisation of the molecule.
If $X$=2 then $sp$; =3 then $s{p^2}$ ; =4 then $s{p^3}$; =5 then $s{p^3}d$ ; =6 then $s{p^3}{d^2}$ ; =7 then $s{p^3}{d^3}$ hybridization.