Halogen gases are a group of interesting elements. They include fluorine, chlorine, bromine, iodine, and astatine. Each one has different colors and densities.

Color:

• Fluorine: Pale yellow
• Chlorine: Yellow-green
• Bromine: Reddish-brown
• Iodine: Dark purple (when solid)
• Astatine: Very rare and unstable, so we don’t know its color very well

Density:

• Fluorine: The lightest, with a density of about 0.0017 grams per cubic centimeter
• Chlorine: A bit denser at 0.0032 grams per cubic centimeter
• Bromine: Much denser, around 3.12 grams per cubic centimeter
• Iodine: Even denser, about 4.93 grams per cubic centimeter

As you look at these gases, you'll notice that as you go down the list, their density gets heavier, and their colors get darker. This change is really interesting!