Which Gas not known as Green House Gas?
Option 2 is the right answer.
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range.
Although contributing to many other physical and chemical reactions, the major atmospheric constituents, nitrogen (N2), oxygen (O2), and argon (Ar), are not greenhouse gases. This is because molecules containing two atoms of the same element such as N2 and O2 and monatomic molecules such as argon (Ar) have no net change in their dipole moment when they vibrate and hence are almost totally unaffected by infrared radiation.
Although molecules containing two atoms of different elements such as carbon monoxide (CO) or hydrogen chloride (HCl) absorb IR, these molecules are short-lived in the atmosphere owing to their reactivity and solubility. Because they do not contribute significantly to the greenhouse effect, they are usually omitted when discussing greenhouse gases.
Hydrogen is a flammable, colorless, odorless, compressed gas packaged in cylinders athigh pressure. It poses an immediate fire and explosive hazard when concentrations exceed 4%. It is much lighter than air and burns with an invisible flame.