Problem 59 - Chemistry: The Central Science

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?

Step-by-Step Solution

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 the orbital are +1/2 and -1/2.

Step 1: (a) Finding possible values of \(m_l\)

The magnetic quantum number \(m_l\) describes the orientation of the orbital in space. It can take on integer values ranging from -l to +l. We are given that l=2 for this orbital, so we need to find the possible values of \(m_l\) within this range. In this case, the possible values of \(m_l\) are -2, -1, 0, 1, and 2.

Step 2: (b) Finding possible values of \(m_s\)

The spin magnetic quantum number \(m_s\) describes the orientation of the electron's spin within the orbital. It can take on two possible values: +1/2 and -1/2. These values correspond to the spin-up and spin-down states of the electron, respectively. Therefore, the possible values of \(m_s\) for this orbital are +1/2 and -1/2.

Key Concepts

Quantum Numbers

When dealing with electrons in atoms, especially hydrogen atoms, quantum numbers are critical as they help define the unique state of an electron. There are four main quantum numbers which describe the energy level, shape, orientation, and spin of the orbital where the electron resides.

1. **Principal Quantum Number ("):** This is the first quantum number and signifies the electron shell or energy level, denoted by "n". For example, if \( n = 4 \), it indicates the electron is in the fourth energy level. The larger the value of \( n \), the farther the electron is from the nucleus and the higher its energy level.2. **Azimuthal Quantum Number (")/Angular Momentum Quantum Number ("):** Represented by "l", this number defines the shape of the orbital. Allowed values of \( l \) range from 0 up to \( n-1 \). For example, with \( l = 0 \) through \( l = 3 \), these correspond to s, p, d, and f orbital shapes, respectively. In our case, \( l = 2 \) describes a "d" orbital.Together, these quantum numbers help paint a more vivid picture of an electron's probable location around a nucleus, aiding in our understanding of atomic interactions.

Magnetic Quantum Number

The magnetic quantum number, denoted as \( m_l \), provides more specific information about the orientation of the orbital in space.

For an electron in an orbital with a given \( l \, ( \text{angular momentum quantum number} ) \), \( m_l \) takes integer values from \( -l \) to \( +l \). Therefore, it essentially describes how an orbital is oriented in the three-dimensional space around the nucleus.

For example, if \( l = 2 \) like in our hydrogen atom problem, the potential values of \( m_l \) can be:

• \( m_l = -2 \)
• \( m_l = -1 \)
• \( m_l = 0 \)
• \( m_l = +1 \)
• \( m_l = +2 \)

These different values indicate the different orientations the "d" orbital can have in space. Understanding \( m_l \) is crucial as it helps us comprehend how electron clouds are distributed within magnetic fields or in atomic arrangements.

Spin Magnetic Quantum Number

The spin magnetic quantum number, noted as \( m_s \), is unique among the quantum numbers as it describes the electron's intrinsic spin rather than aspects of the orbital itself.

Electrons are known to have a fundamental property called "spin," which can be thought of as an angular momentum intrinsic to the electron. Despite being tiny point-like particles, electrons behave like tiny bar magnets. Therefore, \( m_s \) defines the orientation of this spin.Possible values for \( m_s \) are:

• \( +\frac{1}{2} \) (spin-up)
• \( -\frac{1}{2} \) (spin-down)

These two possible values allow each orbital to hold a maximum of two electrons, each with opposite spins. The spin property is crucial for understanding the Pauli exclusion principle, which dictates that no two electrons in an atom can have identical sets of quantum numbers, and plays a vital role in forming chemical bonds and magnetic properties of materials.