Question

One bit of evidence that the present theory of atomic structure is "correct" lies in the magnetic properties of matter. Atoms with unpaired electrons are attracted by magnetic fields and thus are said to exhibit paramagnetism. The degree to which this effect is observed is directly related to the number of unpaired electrons present in the atom. On the basis of the electron orbital diagrams for the following elements, indicate which atoms would be expected to be paramagnetic, and tell how many unpaired electrons each atom contains. a. phosphorus, \(Z=15\) b. iodine, \(Z=53\) c. germanium, \(Z=32\)

Short answer

All three elements exhibit paramagnetism: Phosphorus (P) has 3 unpaired electrons, Iodine (I) has 5 unpaired electrons, and Germanium (Ge) has 2 unpaired electrons.

Step-by-step solution

Write down the electron configuration of each element.

To find the electron configuration of each element, we'll use the atomic number which is provided and follow the Aufbau principle, which states that electrons fill orbitals starting at the lowest available energy level. a. Phosphorus (P), Z = 15 Electron configuration: 1s² 2s² 2p⁶ 3s² 3p³ b. Iodine (I), Z = 53 Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵ c. Germanium (Ge), Z = 32 Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p²

Identify the unpaired electrons in the electron orbital diagrams.

Now that we have the electron configurations, we can determine the number of unpaired electrons in each atom. a. Phosphorus (P): In the 3p³ subshell, there are three unpaired electrons. b. Iodine (I): In the 5p⁵ subshell, there are five unpaired electrons. c. Germanium (Ge): In the 4p² subshell, there are two unpaired electrons.

Determine paramagnetism and the number of unpaired electrons.

Since all three elements have unpaired electrons, all will exhibit paramagnetism. We already identified the number of unpaired electrons in each atom in the previous step. a. Phosphorus (P) is paramagnetic with 3 unpaired electrons. b. Iodine (I) is paramagnetic with 5 unpaired electrons. c. Germanium (Ge) is paramagnetic with 2 unpaired electrons.

Key concepts

Electron Configuration

Understanding the arrangement of electrons in an atom, known as the electron configuration, is critical for predicting an element's chemical behavior, including its magnetic properties. The electrons in an atom fill up various energy levels and sublevels in a specific order. This order is determined by the principle that electrons occupy the lowest available energy state first.

To write down the electron configuration of an element, you start by placing the electrons in the different levels and sublevels according to their increasing energy. For instance, the first two electrons will go into the 1s sublevel, the next two into the 2s sublevel, followed by six electrons into the 2p sublevel, and so on. This pattern continues until all the electrons have been placed. The electron configuration not only helps in determining the reactivity of an element but also its magnetic properties, as it dictates the presence or absence of unpaired electrons, which are predominantly responsible for an atom's magnetic attributes.

Unpaired Electrons

The key to an atom's magnetic properties lies in its unpaired electrons. Atoms have electrons spinning in orbitals, and each orbital can hold a maximum of two electrons with opposite spins. When an orbital is not fully occupied by two electrons, the single electron that is present is called an 'unpaired electron'.

It is these unpaired electrons that contribute to an atom's paramagnetism, meaning they cause an atom to become attracted to external magnetic fields. The more unpaired electrons an atom has, the stronger its paramagnetic properties will be. In the context of the provided exercise, phosphorus has three unpaired electrons in the 3p orbital, iodine has five unpaired electrons in the 5p orbital, and germanium has two unpaired electrons in the 4p orbital, making all of them paramagnetic. This attraction to magnetic fields is a crucial aspect of understanding the magnetic behavior of various substances.

Aufbau Principle

The Aufbau principle is a fundamental tenet of chemistry that guides us in determining an atom's electron configuration. This principle dictates that electrons fill atomic orbitals in order of increasing energy levels, starting from the lowest energy orbital. Aufbau is German for 'building up,' which reflects the sequential filling process of electron shells and subshells.

An easy way to remember this order is by using an Aufbau diagram or by following the 'n + l' rule, where 'n' is the principal quantum number and 'l' is the azimuthal quantum number. Orbitals with a lower 'n + l' value get filled first. However, it is essential to note that there are exceptions to the Aufbau principle due to the complexities of electron interactions and orbital energies, especially for elements with higher atomic numbers. Understanding the Aufbau principle helps students predict the correct electron configurations, which is vital for explaining many chemical properties, including paramagnetism.

Magnetic Properties of Matter

The magnetic properties of matter are largely determined by the behavior of electrons within atoms, particularly the presence of unpaired electrons. Materials can be diamagnetic or paramagnetic based on their atomic structure. Diamagnetic atoms do not have unpaired electrons and are slightly repelled by a magnetic field. In contrast, paramagnetic atoms possess unpaired electrons and are attracted to magnetic fields.

The degree of magnetism that an element exhibits depends on the number of these unpaired electrons. For example, elements with more unpaired electrons, like iodine with five, are more strongly attracted to magnetic fields than those with fewer, such as germanium with two. This property of paramagnetism is vital in numerous applications, including magnetic resonance imaging (MRI) and other technologies that rely on the magnetic properties of materials.