Which of the following quantum numbers describes the size and energy of an orbital?

• A. Spin quantum number (m_s)
• B. Principal quantum number (n)
• C. Magnetic quantum number (m_l)
• D. Azimuthal quantum number (l)

Answer: (B)

Verified step by step guidance

1. Understand that quantum numbers are used to describe the properties of electrons in atoms, specifically their orbitals and spin.
2. Recall the four quantum numbers: Principal quantum number (\(n\)), Azimuthal quantum number (\(l\)), Magnetic quantum number (\(m_l\)), and Spin quantum number (\(m_s\)).
3. Identify the role of each quantum number: \(n\) determines the size and energy level of the orbital; \(l\) defines the shape of the orbital; \(m_l\) specifies the orientation of the orbital in space; and \(m_s\) describes the spin of the electron.
4. Focus on the Principal quantum number (\(n\)), which is a positive integer (1, 2, 3, ...) and directly relates to the energy level and size of the orbital, with higher \(n\) values corresponding to larger orbitals and higher energy.
5. Conclude that the quantum number describing the size and energy of an orbital is the Principal quantum number (\(n\)).