Question

which characteristic is given by the principal quantum number?
orbital size
orbital mass
orbital shape
orbital orientation

Explanation:

To determine the characteristic given by the principal quantum number ($n$), we analyze each option:

• Orbital size: The principal quantum number $n$ is related to the energy level and the size of the orbital. As $n$ increases, the orbital size (the average distance of the electron from the nucleus) increases.
• Orbital mass: Quantum numbers do not describe the mass of the orbital. The mass of electrons (or other particles) is a constant property, and quantum numbers deal with energy levels, shapes, orientations, etc., not mass.
• Orbital shape: The azimuthal quantum number ($l$) determines the shape of the orbital (e.g., $l = 0$ for s - orbital (spherical), $l = 1$ for p - orbital (dumb - bell shaped), etc.).
• Orbital orientation: The magnetic quantum number ($m_l$) determines the orientation of the orbital in space.

So, the principal quantum number gives the orbital size.

Answer:

A. orbital size