* Helium (He): This is the most common example. It's why helium balloons float.
* Hydrogen (H2): Even lighter than helium, but it's highly flammable and not as safe for everyday use.
* Methane (CH4): A component of natural gas, it's also lighter than air.
* Neon (Ne): Used in some signs, it's also less dense than air.
Important Note: Air is a mixture of gases, primarily nitrogen (78%) and oxygen (21%). The density of air varies with temperature and altitude.
