Which set of quantum numbers describes electron orbitals, and what does each indicate?

• A. n, l, m_s, m_l; energy level, subshell shape, orbital orientation, and electron spin.
• B. k, l, m_l, s; energy level, subshell shape, orbital orientation, and spin.
• C. n, l, m_l, m_s; energy level, subshell shape, orbital orientation, and electron spin.
• D. n, l, m_l; energy level, subshell shape, and orbital orientation.

Answer: (C)

The four quantum numbers n, l, m_l, m_s specify an electron’s state in an atom. n determines the energy level and roughly the size of the orbital. l identifies the subshell type and the orbital’s shape (0 for s, 1 for p, 2 for d, 3 for f). m_l gives the orbital’s orientation in space within that subshell, with values from -l to +l. m_s describes the electron’s intrinsic spin direction, with possible values of +1/2 or -1/2. Together, these four numbers uniquely describe the orbital and the spin state of the electron.

This set uses the standard symbols and order, corresponding to energy level, subshell shape, orbital orientation, and electron spin. Other options either replace n with an unfamiliar symbol, omit the spin quantum number, or position the spin value before the orbital orientation, which does not align with how these quantum numbers are defined.