Niels Bohr's atomic model provides specific postulates regarding the behavior of electrons within an atom. Understanding these postulates is key to answering questions about electron movement.

Bohr's Postulates on Electron Orbits

According to Bohr's theory:

• Electrons do not revolve around the nucleus randomly.
• They move in specific, discrete paths known as orbits or shells.
• These orbits are stable, and electrons do not radiate energy while revolving in them.
• Each orbit corresponds to a fixed energy level for the electron.

Analyzing Electron Revolution

Based on Bohr's model:

• Fixed Circular Orbits: Bohr specified that electrons travel in fixed circular paths around the nucleus. These paths are quantized, meaning only certain orbits with specific energies are allowed. These are referred to as shells.
• Elliptical Orbits: The concept of elliptical orbits was introduced later by Arnold Sommerfeld, refining Bohr's model. Bohr's original model focused solely on circular orbits.
• Energy Absorption: Electrons orbit continuously. They absorb energy only when moving from a lower energy orbit to a higher one, and emit energy when moving from a higher to a lower one. They do not orbit *only* when energy is absorbed.
• Location Relative to Nucleus: Electrons orbit the nucleus; they are not located inside the nucleus itself. The nucleus contains protons and neutrons.

Therefore, the most accurate description according to Bohr is that electrons revolve in fixed circular orbits called shells.