Explain why nearly all `H` atoms are in the ground state at room temperature and hence emit no light.

Explanation

According to kinetic theory , the average kinetic energy of atom or molecules in a gas is given by `K = (3//2) kt` where `k = 1.38 xx 10^(-23) j K ^(-1)` is Boltzmane's constant and `T` is Kelvin (absolute) temprature . Room temprature is about `T = 300 K`. Hence
`K = (1)/(2) (1.38 xx 10^(-23)) (300)`
`= 6.2 xx 10^(-21)j`
`= (6.2 xx 10^(-21))/(1.6 xx 10^(-19)) e V`
The energy required to raise an electron from ground state to the next higher state is `13.6 - 3.4 = 10.2 e V`.The everage kinetic energy `(0.04 e V)` of atom is too small to excite an electron from ground state . Any atom in excite state emits photons and elentually falls t the ground state . Once in ground state, collision with other atoms can transfer energy of nearly `0.04 e V` . very high temprature is required to excite electron to upper status.