If you research further, you will find that some gases can easily be seen by the naked human eye. The reason so many cannot be seen is not because they’re invisible, but because of the way our eyes absorb light. Humans can only see things that interact on the visible spectrum (the rainbow.)
Most gas molecules don’t react within that range of visible light making them appear to be invisible. Two gases that can be seen by the naked human eye include chlorine and iodine.
You can see certain gases, such as chlorine and fluorine, but only because they are colored. Most gases are colorless and cannot be viewed. Gas is a material that knows no bounds of its own. Because most gases are hard to observe directly, they are described through the use of four physical properties or characteristics.
These include pressure, volume, number of particles, and temperature. Gas particles are widely disengaged from each other, and they have weaker intermolecular bonds than liquids or solids. Also, there is a place between the absorption spectra of oxygen and water where not much light gets absorbed. We can't see atmospheric gases because they don't have a color in visible range.