What paths or shells do electrons travel around the nucleus in?

• A. Random trajectories around the nucleus.
• B. Well-defined paths known as orbits or shells.
• C. In the nucleus itself.
• D. In magnetic field lines around the atom.

Answer: (B)

The concept being tested is how electrons are arranged around the nucleus. In the simple, widely used model, electrons occupy discrete energy levels called shells or orbits. This picture gives a neat way to think about where electrons are likely to be and how they’re organized by energy. While more advanced quantum mechanics describes electrons in orbitals with probabilistic locations rather than exact paths, the idea of well-defined shells is the standard way this topic is introduced and tested, making it the best answer. The other ideas—random trajectories, being inside the nucleus, or following magnetic field lines—don’t fit how we describe atomic structure in this context.