Question

A certain orbital of the hydrogen atom has \(n=4\) and \(l=2 .\) (a) What are the possible values of \(m_{l}\) for this orbital? (b) What are the possible values of \(m_{s}\) for the orbital?

Short answer

(a) The possible values of \(m_{l}\) for this orbital are \(-2, -1, 0, 1,\) and \(2\). (b) The possible values of \(m_s\) for this orbital are \(+\frac{1}{2}\) and \(-\frac{1}{2}\).

Step-by-step solution

(a) Determine the possible values of \(m_{l}\)

The magnetic quantum number, \(m_l\), can take integer values ranging from \(-l\) to \(+l\). For the given value of \(l=2\), the possible values of \(m_l\) are \(-2, -1, 0, 1,\) and \(2\).

(b) Determine the possible values of \(m_{s}\)

The spin quantum number, \(m_s\), can take two possible values for an electron in any orbital. These values are \(+\frac{1}{2}\) and \(-\frac{1}{2}\). Therefore, the possible values of \(m_s\) for the given orbital are \(+\frac{1}{2}\) and \(-\frac{1}{2}\).

Key concepts

Hydrogen Atom

The hydrogen atom is fundamental in understanding quantum mechanics and atomic physics. It consists of a single proton and a single electron, making it the simplest atom. The electron orbits the proton, influenced by electromagnetic forces, creating distinct energy levels. These energy levels are quantized, corresponding to the electron's specific orbits or shells.
In quantum mechanics, each orbit is characterized by specific quantum numbers: principal (), azimuthal (l), magnetic (\(m_l\)), and spin (\(m_s\)). Each set of quantum numbers describes an electron's unique quantum state in a hydrogen atom, with the principal quantum number, \(n\), indicating the main energy level.
For hydrogen, which has only one electron, these quantum numbers help explain its electronic configuration and predict the atom's behavior under various conditions. Understanding hydrogen's electron structure lays the foundation for more complex atoms.

Magnetic Quantum Number

The magnetic quantum number, denoted as \(m_l\), is one of the four quantum numbers used to describe the unique state of an electron in an atom. It arises due to the quantization of angular momentum.

Understanding \(m_l\)

The magnetic quantum number determines the orientation of an electron's orbital within a subshell. For a given azimuthal quantum number (\(l\)), \(m_l\) can have integer values ranging from \(-l\) to \(+l\). This means for each subshell defined by \(l\), there are \(2l+1\) possible states or orientations.

• When \(l=2\) (as in the original exercise), the possible values of \(m_l\) are \(-2, -1, 0, 1,\) and \(2\).
• These values correspond to the different orientations of the d-orbitals in space.

The concept of the magnetic quantum number is crucial in explaining the fine structure of atomic spectra, as it accounts for the splitting of spectral lines in the presence of a magnetic field.

Spin Quantum Number

The spin quantum number, \(m_s\), represents the intrinsic spin of an electron, a fundamental property analogous to the electron's angular momentum. Electrons have a property called "spin" that can be imagined as a tiny magnetic moment that can point in one of two directions.

Possible Values of \(m_s\)

The spin quantum number has only two possible values:

• \(+\frac{1}{2}\)
• \(-\frac{1}{2}\)

This binary property leads to the two allowed spin orientations, often referred to as "spin-up" or "spin-down."
Electron spin is a critical factor in the Pauli exclusion principle, which states that no two electrons can have the same set of four quantum numbers in an atom. This principle explains why electrons fill atomic orbitals in a specific order and why the periodic table has its particular structure. Understanding the spin quantum number is essential for grasping how electrons behave in magnetic fields and how atoms interact.