Q.

In a mixture of H–He+ gas (He+ is a singly ionized He atom), H atoms and He+ ions are excited to their respective first excited states. Subsequently, H atoms transfer their total excitation energy to He+ ions (by collisions). Assume that the Bohr model of the atom is exactly valid.                [2008]

Q.    The ratio of the kinetic energy of the n=2 electron for the H atom to that of the He+ ion is ______

1 1/4  
2 1/2  
3 1  
4 2  

Ans.

(1)

Kinetic energy for hydrogen or hydrogen-like atom K,

K=-13.6Z2n2⇒K∝Z2

KHKHe+=(ZHZHe+)2=(12)2=14