Question

Which of the following does not have a tetrahedral structure?
(A) \[{\text{SO}}_4^{ - 2}\]
(B) \[{\text{S}}{{\text{F}}_4}\]
 (C) \[{\text{S}}{{\text{O}}_2}{\text{C}}{{\text{l}}_2}\]
 (D) \[{\text{SeO}}_4^{ - 2}\]

Answer 1

Hint: Based on the number of electron pairs that surround the central metal atom, in a molecule, VSEPR theory predicts the shape and geometry of the molecule.

Complete step by step answer: VSEPR theory states that electron pairs repel each other and hence atoms in a molecule will always arrange themselves in a manner such that there is minimum repulsion between their electron pairs. This arrangement directly affects the shape and geometry of the molecule. Based on this assumption, let us take a look at the shapes of the molecules mentioned above –
- \[{\text{SO}}_4^{ - 2}\]

• • \[{\text{S}}{{\text{F}}_4}\]

• \[{\text{S}}{{\text{O}}_2}{\text{C}}{{\text{l}}_2}\]

• \[{\text{SeO}}_4^{ - 2}\]

According to VSEPR theory, there are five groups in molecule i.e. one lone pair and 4 bonds around sulphur. This lone pair is present at one of the equatorial positions than the axial ones. Hence, the shape of the molecule is trigonal bipyramidal and not tetragonal.

Hence, option B is correct.

Additional information: According to the VSEPR theory, the repulsion between two electrons is caused by the Pauli exclusion principle. Some important postulates of VSEPR theory are –
- The electron pairs orient themselves in a way that minimizes the electron-electron repulsion between them and maximizes the distance between them.
- If the central atom of the molecule is surrounded by bond pairs of electrons, then the molecule will be asymmetric in shape.
- If the central atom is surrounded by both lone pairs and bond pairs of electrons, the molecule will have a distorted shape.

Note: Out of the options mentioned above, all molecules except \[{\text{S}}{{\text{F}}_4}\] have four groups that surround the central atom and hence all have tetrahedral shape.