Q.

Consider the Bohr model of hydrogen like atoms, the ratio of the radius of 5th orbit of the electron in Li2+ and He+ is          [2025]

1 32  
2 49  
3 94  
4 23  

Ans.

(4)

r=a0·n2Z

For Li2+r5=a0·253

for He+r5=a0·252

  rLi2+rHe+=23