Problem 96 - Chemistry The Science in Context

Question

Gadolinium(III) ions are used in contrast agents for MRI because they have unpaired electrons. What is the electron configuration for \(\mathrm{Gd}^{3+}\) and how many unpaired electrons does it have?

Step-by-Step Solution

Answer

The Gadolinium (Gd) atom has an electron configuration of [Xe] 4f7 5d1 6s2. When it loses three electrons to form the Gd³⁺ ion, the new electron configuration becomes [Xe] 4f7. In this configuration, there are 7 unpaired electrons in the 4f subshell. Therefore, the Gd³⁺ ion has 7 unpaired electrons.

Step 1: Find the electron configuration of the neutral Gadolinium (Gd) atom

Gadolinium is an element with atomic number 64, which means it has 64 electrons in a neutral state. To find its electron configuration, we can follow the Aufbau principle and fill the orbitals in the order of 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, and so on. In the case of Gadolinium, the electron configuration is given by [Xe] 4f7 5d1 6s2, where [Xe] represents the core electron configuration of Xenon, which is [Xe] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6.

Step 2: Determine the electron configuration of the \(\mathrm{Gd}^{3+}\) ion

The Gadolinium atom has an electron configuration of [Xe] 4f7 5d1 6s2. When we remove three electrons to form the \(\mathrm{Gd}^{3+}\) ion, we should remove them from the outermost orbitals. Firstly, remove two electrons from the 6s orbital, and then remove one from the 5d orbital as 5d has a higher energy level compared to 4f. Thus, the electron configuration of the \(\mathrm{Gd}^{3+}\) ion becomes [Xe] 4f7.

Step 3: Identify the number of unpaired electrons in the electron configuration

The electron configuration of \(\mathrm{Gd}^{3+}\) is [Xe] 4f7. To count the unpaired electrons, we only need to consider the 4f subshell, since all other subshells are fully paired in the [Xe] core configuration. There are 7 electrons in the 4f subshell, which means that there are 7 unpaired electrons in the \(\mathrm{Gd}^{3+}\) ion. In conclusion, the electron configuration for the \(\mathrm{Gd}^{3+}\) ion is [Xe] 4f7, and it has 7 unpaired electrons.

Key Concepts

Gadolinium in Chemistry

Gadolinium, represented by the symbol Gd, is a rare earth metal with atomic number 64. It is part of the lanthanide series, a group of 15 elements known for their unique properties.
These elements are f-block elements, which means they primarily fill their 4f orbitals, giving rise to interesting electron configurations.

• The electron configuration of neutral Gadolinium is [Xe] 4f7 5d1 6s2.
• Gadolinium has diverse uses, but it is best known for its role in magnetic resonance imaging (MRI).

Understanding Gadolinium's electron configuration is crucial for explaining its magnetic properties, making it a valuable element in medical imaging.

Unpaired Electrons

Unpaired electrons are electrons that occupy an orbital alone, without a partner of opposite spin. These electrons are important because they contribute to the magnetic properties of an atom.
In the case of Gadolinium, its ability to have many unpaired electrons in its 4f subshell makes it magnetic.

• The \(\mathrm{Gd}^{3+}\) ion has an electron configuration of [Xe] 4f7.
• This configuration results in 7 unpaired electrons, which is more than most other elements.

The presence of unpaired electrons enables Gd^{3+} to significantly enhance the signals in MRI, thus improving image quality.

Contrast Agents

Contrast agents are substances used in medical imaging to improve the visibility of structures or fluids within the body. In MRI, contrast agents enhance the contrast of the images, allowing doctors to see details more clearly.

• Gadolinium-based contrast agents are widely used due to their magnetic properties.
• These agents work by shortening the relaxation times of protons in the body's tissues.

By increasing the magnetic resonance signals, Gadolinium helps in obtaining clearer, more detailed images, making it easier to diagnose medical conditions.

Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging, commonly known as MRI, is a non-invasive medical imaging technique used to visualize detailed internal structures. It relies on powerful magnets and radio waves to manipulate the spin of protons in body tissues.

• Gadolinium-based contrast agents are used to enhance image quality during MRI scans.
• MRI is preferred for its ability to provide high-contrast images without using ionizing radiation.

The effectiveness of MRI is greatly improved with the use of contrast agents like gadolinium, which increase signal clarity and assist radiologists in providing accurate diagnoses.