Question

An electron in a certain atom is in the \(n=2\) quantum level. List the possible values of \(\ell\) and \(m_{\ell}\) that it can have.

Short answer

The possible values are \((\ell, m_{\ell}) = (0, 0), (1, -1), (1, 0), (1, 1)\)

Step-by-step solution

Determine the possible values of \(\ell\)

The azimuthal quantum number \(\ell\) can be any integer from 0 to \(n-1\). That is, for \(n=2\), possible values of \(\ell\) are \(0, 1\).

Identify the corresponding \(m_{\ell}\) values for each \(\ell\)

For \(\ell = 0\), since the magnetic quantum number, \(m_{\ell}\), can have any integer value between \(-\ell\) to \(\ell\), there's only one possible value: \(0\). For \(\ell = 1\), \(m_{\ell}\) can be \(-1, 0, 1\). Thus, the pairs of \((\ell, m_{\ell})\) are \((0, 0)\), \((1, -1)\), \((1, 0)\), \((1, 1)\).

Key concepts

Azimuthal Quantum Number

In the fascinating realm of quantum mechanics, the behavior of electrons in an atom is fundamentally understood through quantum numbers. The azimuthal quantum number, denoted by \(\ell\), is crucial in determining the shape of an electron's orbitals. Think of orbitals as the clouds of probability where we're likely to find an electron.

For an electron orbiting in the second quantum level (with principal quantum number \(n=2\)), the possible azimuthal quantum numbers are integral values that range from 0 to \(n-1\). This means for \(n=2\), the values of \(\ell\) can be either 0 or 1. Each value of \(\ell\) correlates to a specific type of orbital, with \(\ell=0\) being an s-orbital, which is spherical, and \(\ell=1\) corresponding to p-orbitals, which have a dumbbell shape.

It's not just about numbers—each quantum number paints a picture of an electron’s behavior and environment at the quantum level.

Magnetic Quantum Number

Complementing the azimuthal quantum number, the magnetic quantum number \(m_{\ell}\) fine-tunes our imagery of an electron in its atomic orbital. Where \(\ell\) tells us the shape, \(m_{\ell}\) describes an electron's orientation in space relative to a magnetic field.

This number can take on any integer value between \( -\ell \) and \( \ell \) inclusive. For an azimuthal quantum number \(\ell=0\), there is only one possible magnetic quantum number: 0. This aligns with the spherical symmetry of an s-orbital—there are no orientations to distinguish. However, when \(\ell=1\), which hints at a p-orbital, \(m_{\ell}\) can be \( -1\), \( 0\), or \( 1\), indicating the three possible orientations of a p-orbital in a three-dimensional space.

With this understanding, students should appreciate that the \(m_{\ell}\) values are not arbitrary, but reflect important physical properties of electrons as they occupy different regions around an atom.

Quantum Mechanics in Chemistry

Quantum mechanics is the backbone of modern chemistry, revealing the underlying principles that govern the behavior of electrons in atoms and molecules. Beyond the calculations, it lays the groundwork for predicting chemical properties and understanding reactions at the most fundamental level.

By applying the principles of quantum mechanics, chemists can explain why particular elements behave the way they do and how they will interact with others. The patterns in the periodic table, the shapes of molecules, the types of chemical bonds—these are all dictated by the behavior of electrons as described by quantum numbers. For example, the azimuthal and magnetic quantum numbers allow us to visualize where electrons are most likely to be found, a concept that's directly applied in predicting the geometry of molecules.

This quantum world might seem abstract, but it's enormously practical. From the reaction mechanisms in a high school chemistry lab to the design of new pharmaceuticals, quantum mechanics provides the roadmap for navigating the atomic landscape.