What is the formula for radius r in the nth orbit of an electron?

The electron in an atom is restricted to revolve in certain allowed circular orbit known as stationary orbit. The centripetal force for its motion is provided by electrostatic force of attraction between positively charged nucleus and negatively charged electron.

The formula for radius r in the nth orbit of an electron

 r_n = n²h² / 4π² Kme² Z

r_n = radius of nth orbit

h= Planck’s constant (6.67 x 10^–34 J-s)

n is a positive integer

m= mass of an electron (9.1 x 10–31 Kg)

Z= atomic number (No. of Protons)

K = 1/(4πε₀) = constant = 9 x 10⁹ N m² C^–2     

e = Charge on an electron (1.6 x 10–19 C)