The energy of an electron in the $n^{th}$ orbit of a hydrogen atom is given by:

Based on the equation $E = -2.178 \times 10^{-18} \ J \left( \frac{Z^2}{n^2} \right)$,certain conclusions are written. Which of them is not correct?

When an electron transitions from the $n^{th}$ orbit to the $2^{nd}$ orbit in a $Li^{2+}$ ion,$15$ spectral lines are obtained. What is the value of $n$?

If an electron moves from an excited state to the ground state in multiple steps in the hydrogen spectrum,and the number of lines in the visible region is $4$,then the number of lines in the infrared region is:

For $Li^{2+}$ ion,the ratio of radii $r_2 : r_5$ will be

The radius of $3^{rd}$ orbit of hydrogen atom is $R \text{ pm}$. The radius of $2^{nd}$ orbit of $He^{+}$ ion (in $\text{pm}$) is