ClF5 at room temperature is a

🧠 Determine the geometry of $\ce{ClF5}$ using VSEPR: Cl has 7 valence electrons, 5 bonds to F, leaving 1 lone pair.

Steric number = 5 + 1 = 6 → octahedral electron geometry → with 1 LP, the molecular shape is square pyramidal (lone pair occupies one axial position of an octahedron, pushing 4 equatorial F atoms into a square base with 1 apical F).

$\ce{ClF5}$ is indeed a colourless liquid at room temperature (boiling point ≈ −13.1 °C, so it is a liquid at room temperature near its bp; sometimes cited as liquid at 25 °C under moderate pressure, or near-liquid at RT). The key fact tested here is its square pyramidal geometry.

$\boxed{\text{Answer: (d) Colourless liquid with square pyramidal geometry}}$