152.

Lifetimes of the molecules in the excited states are often measured by using pulsed radiation source of duration nearly in the nano second range. If the radiation source has the duration of 2 ns and the number of photons emitted during the pulse source is 2.5 x 10¹⁵, calculate the energy of the source.

Electromagnetic radiation of wavelength 285 nm is just sufficient to ionise the potassium atom. What is the ionization energy of potassium (in kJ mol^-1) ?

Give essential features of Bohr's model of atom.

The energy associated with the first orbit in the hydrogen atom is - 2.18 x 10^-18J atom^-1. What is the energy associated with the fifth orbit?

(ii) Calculate the radius of Bohr’s fifth orbit for the hydrogen atom.

Calculate the radius of Bohr's fifth orbit for hydrogen atom.

Calculate the energy associated with first orbit of He⁺. What is the radius of this orbit? 

How much energy is required to ionise a H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom (energy required to remove the electron from n = 1 orbit).