Symbolized by n, indicates the main energy level occupied by the electron.

• A. Quantum numbers
• B. Principle quantum number
• C. Orbital
• D. Continuous spectrum

Answer: (B)

The main concept is that n is the principal quantum number, which labels the main energy level or shell an electron occupies. It is an integer (1, 2, 3, …) and largely sets the energy and size of the orbital in the basic hydrogen-like picture. In that model, the energy depends primarily on n, with higher n meaning electrons are less tightly bound and energy levels become closer together. Other quantum numbers describe more details: l (orbital shape) and m_l (orientation) alongside m_s (spin) define specific orbitals and their properties, but they do not alone specify the main energy level. An orbital is a region of space associated with a particular set of quantum numbers, not just n by itself. The term continuous spectrum refers to a range of wavelengths without discrete lines, which isn’t about the quantized energy levels described by n.