ClF$$_5$$ at room temperature is a

We need to determine the physical state and geometry of ClF$$_5$$ at room temperature.

Chlorine has 7 valence electrons. In ClF$$_5$$, Cl forms 5 bonds with F atoms using 5 electrons, leaving 1 lone pair. The total electron pairs around Cl are 5 bond pairs + 1 lone pair = 6 pairs. So the electron geometry is octahedral, and with one lone pair, the molecular geometry is square pyramidal.

Now for the physical state, ClF$$_5$$ is a colourless liquid at room temperature. Interhalogen compounds with higher number of atoms tend to be liquids or solids.

Hence, the correct answer is Option D: Colourless liquid with square pyramidal geometry.