According to Bohr's model, the radius of the second orbit of helium atom is

0.53 Å 1.06 Å 2.12 Å 0.265 Å

1.06 Å

$r=\frac{n^2}{Z}\left(r_0\right) ; \Rightarrow r_{(n=2)}=\frac{(2)^2}{2} \times 0.53=1.06 Å$