When discussing energy absorption by atoms, the focus is primarily on electrons rather than protons because electrons play a dominant role in determining the chemical and physical properties of atoms. Protons, on the other hand, are located within the atomic nucleus and are much more tightly bound compared to electrons.
Electrons are negatively charged particles that orbit around the atomic nucleus in discrete energy levels or shells. These energy levels correspond to specific quantized energy values, and electrons can absorb or release energy to transition between these levels. When an electron absorbs energy, it can move to a higher energy level or transition to an excited state.
The absorption of energy by electrons is responsible for various phenomena, such as the absorption of light by atoms, leading to the creation of spectral lines. For example, when an electron absorbs a photon with an energy corresponding to the energy difference between two electron energy levels, it can be promoted to a higher energy level. This absorption of energy by electrons is the basis of many spectroscopic techniques used to study atoms and molecules.
Protons, on the other hand, are located in the atomic nucleus and are much more tightly bound by the strong nuclear force. The energy required to affect protons is typically orders of magnitude higher compared to electrons. Proton energies are typically involved in nuclear reactions, such as fusion or fission, rather than the atomic-scale processes that involve electron energies.
While protons can interact with energy in certain contexts, such as in high-energy physics or nuclear reactions, their energy absorption or excitation is not as commonly discussed when considering the chemical or physical behavior of atoms in everyday situations.