\({r_3}{\mkern 1mu} {\mkern 1mu} = {\mkern 1mu} {\mkern 1mu} 0.529 \times \frac{{3 \times 3}}{3}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} = {\mkern 1mu} {\mkern 1mu} 0.529 \times 3\mathop {{\text{ }}A}\limits^o {\mkern 1mu} = {\mkern 1mu} {\mkern 1mu} 1.587{\mkern 1mu} \mathop {{\text{ }}A}\limits^o \)
(આપેલું છે : ઈલેકટ્રોનનું દળ $=9.1 \times 10^{-31} \,kg$, પ્લાન્ક અચળાંક $h =6.63 \times 10^{-34}\, Js$ )