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JEE Main levelSingle correct optionDifficulty 2 of 3ev073

Nitrogen and oxygen make up about 99% of dry air but are not greenhouse gases. The reason is that

Athey are too light to be heated by sunlight
Bthey are chemically inert at all temperatures
Ctheir vibration does not change the dipole moment, so they do not absorb infrared radiation
Dthey absorb all the incoming UV and so no IR is left

Answer: C

A molecule absorbs infrared only if its vibration changes the dipole moment. The homonuclear molecules

N X_{2}

and

O X_{2}

have no dipole at any stretch, whereas

CO X_{2}

,

CH X_{4}

and

N X_{2} O

do.

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