Question

Using an orbital box diagram and noble gas notation, show the electron configurations of uranium and of the uranium(IV) ion. Is either of these paramagnetic?

Short answer

Both uranium and uranium(IV) are paramagnetic due to unpaired electrons.

Step-by-step solution

Understanding the Problem

To solve this exercise, we need to find the electron configurations for uranium (U) and its ion uranium(IV) (U⁴⁺). We will use both the orbital box diagram and noble gas notation, and determine if either configuration has unpaired electrons, which is indicative of being paramagnetic.

Identifying Uranium's Atomic Properties

Uranium has an atomic number of 92, which means a neutral uranium atom has 92 electrons. Uranium belongs to the actinide series and is expected to fill its 5f subshell.

Electron Configuration for Uranium (U)

Using the noble gas notation, we start from the nearest noble gas, radon ( [{Rn]} ) and continue the electron configuration: [{Rn}] 5f^3 6d^1 7s^2. In orbital box diagrams, 5f has three boxes filled with single electrons, 6d has one box filled, and 7s has two boxes filled.

Electron Configuration for Uranium(IV) (U⁴⁺)

To find the configuration of U⁴⁺, we remove four electrons from uranium's configuration, typically from the outermost subshells. Removing from [7s^2, 6d^1, and 5f^1] leaves us with: [{Rn}] 5f^2.

Analyzing Paramagnetism

Check for unpaired electrons. The uranium configuration [{Rn}] 5f^3 6d^1 7s^2 has unpaired electrons (three in 5f and one in 6d), hence it's paramagnetic. The U⁴⁺ configuration [{Rn}] 5f^2 also has unpaired electrons, so it is paramagnetic too.

Key concepts

Uranium

Uranium is a heavy metal with the chemical symbol U and an atomic number of 92. It is a member of the actinide series in the periodic table, which consists of 15 elements. This category is known for having elements with electrons filling their 5f orbitals, thus influencing their chemical properties.

The primary use of uranium is as fuel in nuclear reactors. Its unique properties also make it suitable for scientific and medical research. Uranium's remarkable capability to undergo fission makes it essential for generating nuclear energy. Understanding uranium's electron configuration is crucial to accessing information about its reactivity and relating it to applications in nuclear physics.

When discussing its electron structure, a neutral uranium atom has 92 electrons, requiring an understanding of how these electrons are distributed among different orbitals, especially the partially filled 5f orbitals.

Paramagnetism

Paramagnetism is a property of certain materials that causes them to be attracted into an external magnetic field. This characteristic arises from the presence of unpaired electrons in the materials' atomic or molecular structure.

- **Unpaired Electrons**: In paramagnetic substances, electrons are not completely paired. Electrons behave like tiny magnets due to their spin, and when they are unpaired, they contribute to the magnetic properties of the atom.
- **Magnetic Field Interaction**: When subjected to an external magnetic field, paramagnetic materials will have their magnetic moments aligned in the direction of the field, creating an attraction.
In the context of uranium, both a neutral uranium atom and the uranium(IV) ion have unpaired electrons. This means both configurations exhibit paramagnetism. For uranium, the electron configurations with unpaired electrons contribute to properties that are of interest in magnetic and electronic applications.

Orbital Box Diagram

An orbital box diagram visually represents the electron configuration of an atom. It shows the arrangement of electrons in their respective orbitals using boxes or squares.

- **Boxes for Orbitals**: Each box represents a single orbital, and each arrow within a box symbolizes an electron. The direction of the arrow indicates the electron's spin.
- **Filling Order**: Electrons fill lower-energy orbitals first before moving to higher-energy orbitals. This follows the Aufbau principle.
- **Example with Uranium**: For uranium's electron configuration, \(\text{{[Rn]}} 5f^3 6d^1 7s^2\) is expressed using the orbital box diagram, illustrating the three partially filled 5f boxes, one filled 6d box, and two filled 7s boxes.
Creating an orbital box diagram helps visualize how electrons occupy various orbitals and provides insight into properties such as magnetism.

Noble Gas Notation

Noble gas notation is a streamlined way of writing electron configurations by starting from the electron configuration of the nearest noble gas preceding the element in the periodic table.

- **Simplification**: This method simplifies the notation by reducing the lengthy list of occupied orbitals to only those beyond the noble gas core. It saves time and space.
- **Example with Uranium**: Instead of listing all 92 electrons for uranium, one can use radon \(\text{{[Rn]}}\) as its core, followed by \(5f^3 6d^1 7s^2\), to represent the electrons Uranium has beyond radon.
Utilizing noble gas notation is not only more concise but also makes it easy to identify the valence electrons that determine the reactivity and bonding behavior of the element.