# Why is boron or carbon solids and chlorine a gas at room temperature

I know different compounds have different states at room temperature because of inter-molecular forces ( dipole-dipole force, hydrogen bonding, and London dispersion forces).

But how do they act on elements? Is there any other inter-moleculer force.

The reason why boron and carbon are solids at room temperature because of their structure.

Both carbon and boron form giant covalent structures, meaning a lot of energy has to be put into break the bonds between atoms and turn into a liquid. A example of this would be diamond - here each carbon atom is covalently bonded to 4 others meaning no inter-molecular force exist between the atoms are these are not small simple molecules.

Chlorine however is a small simple molecule $$\ce{Cl2}$$. Here only van der Waals forces hold the molecules together meaning that they can easily be broken - hence why its a gas at room temp.

So elements boiling point is always dictated by inter-molecular forces as it is dependent on its structure. some structures will allow inter-molecular forces to arise giving rise to relatively low bp and mp, while others have giant structures that doesn't give rise to inter-molecular forces only intra-molecular forces.