Assume that the electron in He
+
ion is excited to the second orbit (n = 2). Calculate the
following:
(i) the radius of the orbit
(ii) the velocity of the electron
(iii) the potential energy of the electron, and
(iv) the kinetic energy of the electron

Answer :

R = 0.512x10^(-10)(n^2/z) metre
n is orbit no. 
z is atomic number.
here, n=2, z=2
v=2.18X10^6(z/n) ms^(-1)
E=31.6 (Z^2/ n^2) ev(electron volt)
potential energy= 2E
kinetic energy= -E