Question

Which electronic level would allow the hydrogen atom to absorb a photon but not to emit a photon?
A. $3s$
B. $2p$
C. $2s$
D. $1s$

Answer 1

The atomic number of hydrogen is 1. So write the electronic configuration of hydrogen first to get the energy levels present. And then find in which energy level of hydrogen, it is not feasible to emit a photon.

Complete step by step answer:
Hydrogen is a colorless, tasteless, odorless, and highly flammable gas. The hydrogen molecule has 2 atoms of hydrogen i.e. di-atomic. The atomic number of hydrogen is 1 and represented using the symbol H. Hydrogen is the lightest element in the periodic table.
The electronic configuration of hydrogen is $1{s^1}$
As we can see, the hydrogen atom has only one energy level in its configuration. 1s is the lowest energy level possible.
So this orbital can absorb photons but cannot emit a photon. Because by emitting a photon electron will go from higher energy level to lower energy level. $1s$ is the possible lowest energy level and we cannot go to a lower level. But it can absorb a photon as the electrons can be transferred from $1s$ to $2s$ i.e. lower energy level to higher energy level.
So the electronic level would allow the hydrogen to absorb a photon but not to emit a photon is $1s$

The correct option is Option D, $1s$.

Additional Information: Hydrogen can be used in cells to generate electricity, heat, and power. It is most commonly used in fertilizers and petroleum refinement.

Note:
A Photon is an elementary particle. Do not confuse a photon with an electron. An electron is a particle with a negative charge whereas a photon does not have any charge. An electron has a charge and a mass but the photon is energy and does not have any charge and mass.