JEE Main · 2021 · 16 Mar 2021 · Shift 2 · Environmental Chemistry

A gas warms the atmosphere only if it absorbs infrared radiation, and that demands a vibration during which the dipole moment changes. Carbon dioxide has bending and asymmetric stretching modes that do this, water vapour and methane are also infrared active, and all three trap the radiation leaving the earth. Oxygen is homonuclear and diatomic, so its single stretching vibration leaves the dipole moment at zero throughout and the molecule is transparent in the infrared. The greenhouse gases in the list are carbon dioxide, water vapour and methane.