Sulfur hexafluoride (SF6) is heavier than air due to its high molecular weight and density.

Here's a breakdown:

* Molecular Weight: SF6 has a molecular weight of 146.06 g/mol, significantly higher than the average molecular weight of air (approximately 29 g/mol). This is because it contains six fluorine atoms, which are relatively heavy.

* Density: The density of a gas is directly related to its molecular weight. Since SF6 has a higher molecular weight, it has a higher density than air. This means that a given volume of SF6 will weigh more than the same volume of air.

To put it simply: SF6 molecules are much heavier than the average air molecule, making SF6 denser and heavier.

This property makes SF6 useful in various applications, such as:

* Insulating gas in electrical equipment due to its high dielectric strength.

* Medical imaging as a contrast agent.

* Fire suppression systems due to its non-flammable nature.

Let me know if you have any other questions!