When the electron in an atom makes a transition from a lower energy level to a higher energy level, what happens to its energy?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → It increases.
The energy of the hydrogen atom in the Bohr model is least for n = 1. It becomes larger and larger in the outer orbits, \( E_n=-13.6\,\mathrm{eV}/n^{2} \).
Option (1) It increases. — Correct. A higher level has a less negative, that is larger, energy. So the electron can reach it only by receiving energy, for example in a collision or by absorbing a photon of the right frequency. Its energy then increases.
Option (2) It decreases. — Incorrect. The energy decreases only in a transition from a higher level to a lower one, when the difference is given out as a photon.
Option (3) It depends upon the energy level to which the transition is made. — Incorrect. Every higher level has more energy than the starting level. So the energy rises whichever higher level is reached. Only the amount of the rise depends on the final level.
NCERT (2026-27):
Energy Levels – “The energy of an atom is the least (largest negative value) when its electron is revolving in an orbit closest to the nucleus i.e., the one for which n = 1. For n = 2, 3, ... the absolute value of the energy E is smaller, hence the energy is progressively larger in the outer orbits.”
Energy Levels – “At room temperature, most of the hydrogen atoms are in ground state. When a hydrogen atom receives energy by processes such as electron collisions, the atom may acquire sufficient energy to raise the electron to higher energy states.”