Which of the following is not tetrahedral in shape?

The correct answer is Option (3) → \(SF_4\)

By VSEPR theory, the shape of a molecule depends on the number of bond pairs and lone pairs around the central atom. Four bond pairs and no lone pair give a tetrahedral shape (sp³).

• Option (1) \(NH_4^+\) — Tetrahedral. N has four N–H bond pairs and no lone pair (the lone pair of \( \ce{NH3} \) has bonded to \( \ce{H^+} \)); sp³.

• Option (2) \(SiCl_4\) — Tetrahedral. Si has four Si–Cl bond pairs and no lone pair; sp³.

• Option (3) \(SF_4\) — Not tetrahedral (see-saw). Sulphur uses four of its six valence electrons in the four S–F bonds and keeps one lone pair. Five electron pairs give sp³d hybridisation and a trigonal bipyramidal arrangement with the lone pair in an equatorial position, so the shape is a see-saw.

• Option (4) \(CH_4\) — Tetrahedral. C has four C–H bond pairs and no lone pair; sp³, bond angle 109.5°.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Reactivity towards Halogens – …