Formula for velocity of electrons in orbit is

Vn= Ze^2/2nh

e= charge on electron

Z= Atomic number

n= no. orbit

h= Plank’s constant

First orbit of the H atom given as follows:

V= x

V1= 1*e^2/2*1*h

=e^2/2h=x

For the 3rd orbit

V3= 1*e^2/2*3*h

=e^2/6h=1/3x

(e2/2h*1/3=x*1/3 becomese2/6h=1/3x).

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