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 equation or formula for Bohr model for first postulate is given as,
mv2 / rn = KZe2 / rn2
m= mass of an electron (9.1 x 10–31 Kg)
v = Frequency of radiation which is either emitted or absorbed.
rn = radius of nth orbit
Z= atomic number (No. of Protons)
e = charge of electron.
K = 1/(4πε0) = coulomb’s constant = 9 x 109 N m2 C–2