Question

For absorption and emission spectra of atoms, which one of the following particles changes energy level?
A) Alpha
B) Electron
C) Neutron
D) Photon
E) Proton

Answer 1

Hint: To find the particles which change energy levels, we have to observe the characteristic behavior of each particle in an atom and try to identify which particle is bound to the atom lightly and can escape the nuclear force to change the energy levels. Also, try to figure out what happens when these particles change energy levels.

Complete answer:
An atom is mainly made up of three particles: protons, neutrons and electrons. In the nucleus of the atom, protons and neutrons are present. Around the nucleus, electrons are present in different electron shells. The protons and the neutrons are heavier particles as compared to electrons and are bound together by a strong nuclear force. Therefore, protons and neutrons can’t change their energy levels.
Photons are massless particles which are also a fundamental particle of light. They act as both particles as well as waves. On the other hand, alpha particles are positively charged particles that consist of two protons and two neutrons bound together in a particle. It doesn’t contain any electron which can take part in changing the energy levels.
Therefore, electrons present on the outermost shell of the atom, also known as the valence electrons change the energy levels as they are lighter and are lightly bound to the nucleus.
Therefore, option (B) is correct.

Note:
When electrons absorb energy, they move from lower energy levels to higher energy levels. But, higher energy levels are unstable and electrons attain stability by radiating the energy absorbed and returning to the ground state. The spectrum formed by the frequencies of this emitted energy is known as the emission spectrum. Photons are emitted when there is a transition from the excited state to the ground state. Different wavelengths of light waves produce different colors.
The absorption spectrum is formed when electrons absorb energy and get excited to higher energy levels. Often dark bands are observed in the absorption spectrum.