The quantum theory was first used to explain the structure of the atom,which was proposed by .......

Arrange the following wavelengths $(\lambda)$ of given emission lines of $H$ atoms in increasing order:
$(a) \ n = 3 \xrightarrow{\lambda_1} n = 1$
$(b) \ n = 12 \xrightarrow{\lambda_3} n = 10$
$(c) \ n = 5 \xrightarrow{\lambda_2} n = 3$
$(d) \ n = 22 \xrightarrow{\lambda_4} n = 20$
Choose the correct option.

The radius (in $\mathring{A}$) of the $3^{rd}$ Bohr orbit in $Li^{2+}$ ion is closest to $......$ [Given: Atomic number of $Li = 3$]

The energy level for $A^{(+z-1)}$ is given by which of the following expressions?

The radius of the first excited state of a Helium ion $(He^+)$ is given by (where $a_0$ is the radius of the first stationary state of the hydrogen atom):

The wavenumber of the first line $(n_2=3)$ in the Balmer series of hydrogen is $\bar{\nu}_1 \ cm^{-1}$. What is the wavenumber (in $cm^{-1}$) of the second line $(n_2=4)$ in the Balmer series of $He^{+}$?