What is the energy (in J atom⁻¹) required for the following process?

Li²⁺ (g) → Li³⁺ (g) + e⁻

(Take the ionization energy for the H atom in the ground state as $2.18 \times 10^{−18} \text{ J atom}^{−1}$)

The wavelength of photon 'A' is 400 nm. The frequency of photon 'B' is $10^{16} \ \text{s}^{-1}$. The wave number of photon 'C' is $10^4 \ \text{cm}^{-1}$. The correct order of energy of these photons is :

The wave numbers of three spectral lines of H atom are considered. Identify the set of spectral lines belonging to Balmer series.

( $\mathrm{R}=$ Rydberg constant)

Figure 1. electron probability density for 2 s orbital

Figure 2. wave function for 2s orbital

Which of the following point in Figure 2 most accurately represents the nodal surface as shown in Figure 1?