Q.

The radius of innermost orbit of hydrogen atom is 5.3×10-11m. What is the radius of third allowed orbit of hydrogen atom         [2023]
 

1 1.59 Å  
2 4.77 Å  
3 0.53 Å  
4 1.06 Å  

Ans.

(2)

Given, r1=5.3×10-11m

Radius of nth orbit of Hydrogen atom is, rn=0.53×n2ZÅ

The radius of the third allowed orbit of hydrogen atom is, r3=0.53×(3)21Å

r3=47.7×10-11m;  r3=4.77×10-10m or 4.77 Å