Q.

Radius of the first excited state of Helium ion is given as: a0 radius of first stationary state of hydrogen atom.             [2025]

1 r=2a0  
2 r=4a0  
3 r=a02  
4 r=a04  

Ans.

(1)

r=a0n2Z

For He+ ion, Z = 2 and for first excited state, n = 2.

r=a0222=2a0