- Energy Levels in an Atom Definition: Energy levels in an atom are defined as specific orbits around the nucleus where electrons reside, each with a distinct energy amount.
- Electron Orbits: Electrons move in fixed paths or orbits around the nucleus, and these paths are the energy levels of the atom.
- Energy Absorption and Emission: Electrons absorb energy to move to higher energy levels and emit energy when returning to their original levels.
- Quantized Energy: Electrons can only absorb or emit specific, quantized amounts of energy corresponding to the difference between energy levels.
- Electron Excitation and Conduction: Electrons in outer shells require less energy to get excited and can become free, contributing to electrical conduction in materials like metals.
Atoms are the building blocks of all materials. Each atom has a central nucleus made up of protons and neutrons, with electrons revolving around it. Electrons do not follow the same path, but each has its own specific orbit, called an energy level. These energy levels are fixed paths where electrons move around the nucleus.
This is because, each of them possess a dedicated amount of energy which is expressed in terms of an integral multiple of the equation 
Where h is the Planck’s constant and υ is the frequency.
Different energy states in an atom have specific energies measured in electron volts (eV). As electrons move further from the nucleus, their energy increases. For example, an electron in the first energy state (E1) has an energy of -13.6 eV, while in the second state (E2) it has -3.4 eV. Eventually, an energy level (E∞) is reached where the energy is 0 eV.
When external energy, such as light, is supplied to a material, electrons in the atoms absorb this energy. Electrons can only absorb specific amounts of energy. If an electron in the energy state E1 absorbs 4 eV of energy, its total energy changes, meaning it can’t stay in the same energy level.
due to which it can no longer stay in the energy level E1 which has its energy as -13.6 eV. Moreover it cannot see any other level which has an energy equivalent to what it has. This makes it lose its track!
On the other hand, if this electron absorbs energy of 10.2 eV, then its increased energy would be
This is nothing but the energy possessed by the level E2, meaning which the electron which was formerly in E1 is now in the energy level E2. In other words, we say that this electron has made a transition from the level E1 to the level E2 which inturn leads to an excited atom. However the electron cannot stay in this unstable state for long. It will soon return to its original state by making a transition from the level E2 to the level E1. But an important point to be noted here is the fact that while doing so, the electron emits an energy of 10.2 eV (which is same as that of the absorbed) in the form of electromagnetic waves.
From the discussion presented, it is evident that the electrons are permitted to absorb (or equivalently emit) only quantized amounts of energy. The amount of this energy is nothing but the difference in the energies of the levels among which the transition occurs. Next, from Figure 2, it is seen that this difference between the energy states goes on decreasing as one moves away from E1 i.e. …
This means that the electrons in the outermost shells require less amount of energy to get excited than those present in the innermost shells. This is in accordance with the well known fact that the electrons present near the nucleus are strongly bonded to the atoms rather than the ones which are present away from it.
Although we have explained the process of excitation, the same mode of argument holds good even for the case of liberation.This is because, we can assume that the electron when gets excited to the energy level with an energy of 0 eV (E∞), it would be completely free from the attractive force of the atom’s nucleus. It is these free electrons which contribute for conduction in the case of materials like metals.
