Problem 49 - Chemistry and Chemical Reactivity

Question

The magnet in the following photo is made from neodymium, iron, and boron. (a) Write the electron configuration of each of these elements using an orbital box diagram and noble gas notation. (b) Are these elements paramagnetic or diamagnetic? (c) Write the electron configurations of \(\mathrm{Nd}^{3+}\) and \(\mathrm{Fe}^{3+}\) using orbital box diagrams and noble gas notation. Are these ions paramagnetic or diamagnetic?

Step-by-Step Solution

Answer

Neodymium, iron, and boron are paramagnetic; Nd^{3+} and Fe^{3+} are also paramagnetic.

Step 1: Electron Configuration of Neodymium (Nd)

Neodymium has the atomic number 60, so it has 60 electrons. Using noble gas notation: - Previous noble gas: [Xe] - Continuing from xenon: - 4f: ⬛⬛⬛⬛⬛ (5 electrons) - 6s: ⬛⬛ (2 electrons) The electron configuration in noble gas notation is [Xe] 4f^4 6s^2.

Step 2: Electron Configuration of Iron (Fe)

Iron has the atomic number 26, giving it 26 electrons. Using noble gas notation: - Previous noble gas: [Ar] - Continuing from argon: - 3d: ⬛⬛⬛⬛⬛ (5 electrons) - 4s: ⬛⬛ (2 electrons) The electron configuration in noble gas notation is [Ar] 3d^6 4s^2.

Step 3: Electron Configuration of Boron (B)

Boron has the atomic number 5, giving it 5 electrons. Using noble gas notation: - Previous noble gas: [He] - Continuing from helium: - 2s: ⬛⬛ (2 electrons) - 2p: ⬛ (1 electron) The electron configuration in noble gas notation is [He] 2s^2 2p^1.

Step 4: Determine Magnetism - Neodymium (Nd)

Neodymium with unpaired 4f electrons is paramagnetic because unpaired electrons contribute to magnetic properties.

Step 5: Determine Magnetism - Iron (Fe)

Iron has unpaired electrons in the 3d sublevel, so it is paramagnetic.

Step 6: Determine Magnetism - Boron (B)

Boron has one unpaired electron in the 2p sublevel, making it paramagnetic.

Step 7: Electron Configuration of Nd^{3+}

When neodymium loses three electrons to form Nd^{3+}, it loses them from the 6s and 4f orbitals: - Configuration: [Xe] 4f^3. - Three 4f electrons remain unpaired, making Nd^{3+} paramagnetic.

Step 8: Electron Configuration of Fe^{3+}

When iron loses three electrons to form Fe^{3+}, it loses from both the 4s and 3d orbitals: - Configuration: [Ar] 3d^5. - With half-filled d orbitals, electrons are unpaired, making Fe^{3+} paramagnetic.

Key Concepts

Paramagnetism

Paramagnetism is a type of magnetism where certain materials show weak attraction towards a magnetic field due to the presence of unpaired electrons. These unpaired electrons have magnetic moments that do not cancel out, allowing the material to become temporarily magnetized when an external magnetic field is applied. This phenomenon occurs because the magnetic moments align with the external magnetic field.

The concept can be easily understood by looking at the electron configuration of atoms or ions. For example:

• Neodymium (Nd): The electron configuration in noble gas notation is [Xe] 4f^4 6s^2. Neodymium has unpaired electrons in its 4f orbitals, leading to paramagnetism.
• Iron (Fe): With an electron configuration of [Ar] 3d^6 4s^2, iron also has unpaired electrons, making it paramagnetic.
• Boron (B): Even with a much simpler configuration of [He] 2s^2 2p^1, boron exhibits paramagnetism due to its single unpaired electron.

Materials that are paramagnetic are usually only weakly attracted to magnetic fields, and this quality results from the intrinsic magnetic moments of the unpaired electrons.

Diamagnetism

Diamagnetism, conversely, occurs in materials where all electrons are paired. In this state, the magnetic moments of the electrons cancel out completely, resulting in no net magnetic moment. Therefore, when exposed to a magnetic field, these materials actually create an induced magnetic field in the opposite direction, which leads to a very weak repulsion.

Unlike paramagnetism, diamagnetism persists in all substances since electronic orbital motion inherently produces a small magnetic moment. However, it is most noticeable in materials where no other form of magnetism interferes. All electrons spinning in opposite directions create equal but opposite magnetic fields that neutralize each other's effects. Consequently, substances that exhibit primarily diamagnetic behavior do not retain any magnetization in the absence of an external magnetic field.

Examples of diamagnetic substances include materials like bismuth and copper. It's important to understand that diamagnetism is a universal property of matter, but it often gets overshadowed by paramagnetism or ferromagnetism in substances with unpaired electrons or magnetic domains.

Noble Gas Notation

Noble gas notation offers a shorthand way to write electron configurations that simplifies understanding. By using the electron configuration of the previous noble gas as a reference point, we can quickly depict the electrons beyond those in the noble gas.

This method helps to focus on the valence electrons or the outermost electrons which are essential for determining chemical behavior. For example:

• Neodymium (Nd): Instead of listing all electrons from the beginning, we write [Xe] 4f^4 6s^2, which shows electrons beyond xenon.
• Iron (Fe): Simplified as [Ar] 3d^6 4s^2, it highlights the electrons after argon.
• Boron (B): Expressed as [He] 2s^2 2p^1, shows electrons beyond helium.

Employing noble gas notation helps in easily recognizing unpaired electrons that contribute to phenomena like paramagnetism.

Overall, using noble gas notation streamlines the process of writing electron configurations, making it more efficient and less cumbersome, especially for elements with a large number of electrons.