Which characteristic of an electron in an atom is determined by the principal quantum number (n)?

• A. The orientation of the orbital in space
• B. The shape of the orbital
• C. The spin direction of the electron
• D. The energy level or shell of the electron

Answer: (D)

Verified step by step guidance

1. Understand that the principal quantum number, denoted as \(n\), is one of four quantum numbers used to describe the unique quantum state of an electron in an atom.
2. Recall that \(n\) primarily determines the energy level or shell in which the electron resides, which corresponds to the average distance of the electron from the nucleus.
3. Recognize that other quantum numbers describe different characteristics: the azimuthal quantum number (\(l\)) determines the shape of the orbital, the magnetic quantum number (\(m_l\)) determines the orientation of the orbital in space, and the spin quantum number (\(m_s\)) describes the spin direction of the electron.
4. Therefore, the characteristic determined by the principal quantum number \(n\) is the energy level or shell of the electron.
5. Summarize that \(n\) defines the main energy level, which influences the electron's energy and size of the orbital, but not its shape, orientation, or spin.