Problem 74 - Chemistry The Molecular Science

Question

(a) In the first transition series (in row four of the periodic table), which elements would you predict to be diamagnetic? (b) Which element in this series has the greatest number of unpaired electrons?

Step-by-Step Solution

Answer

(a) Cu and Zn are diamagnetic. (b) Mn has the greatest number of unpaired electrons.

Step 1: Identify Transition Elements

In the first transition series (row four of the periodic table), the elements are from Scandium (Sc) to Zinc (Zn). This includes: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn.

Step 2: Determine Electronic Configurations

The electronic configurations for these elements are as follows:- Sc: [Ar] 3d\(^1\) 4s\(^2\)- Ti: [Ar] 3d\(^2\) 4s\(^2\)- V: [Ar] 3d\(^3\) 4s\(^2\)- Cr: [Ar] 3d\(^5\) 4s\(^1\)- Mn: [Ar] 3d\(^5\) 4s\(^2\)- Fe: [Ar] 3d\(^6\) 4s\(^2\)- Co: [Ar] 3d\(^7\) 4s\(^2\)- Ni: [Ar] 3d\(^8\) 4s\(^2\)- Cu: [Ar] 3d\(^10\) 4s\(^1\)- Zn: [Ar] 3d\(^10\) 4s\(^2\) These configurations will help us determine if an element is diamagnetic based on the filling of electrons in the d-orbital.

Step 3: Identify Diamagnetic Elements

An element is diamagnetic if all electrons are paired within its electronic configuration. From the electronic configurations, Cu and Zn are diamagnetic since Cu: [Ar] 3d\(^10\) 4s\(^1\) and Zn: [Ar] 3d\(^10\) 4s\(^2\) have fully paired d-electrons.

Step 4: Determine Maximum Unpaired Electrons

The element with the greatest number of unpaired electrons will have the highest number of electrons not paired in the d-orbital. Mn: [Ar] 3d\(^5\) 4s\(^2\) has five unpaired electrons in the 3d subshell, which is the maximum among this series.

Key Concepts

Electron Configuration

Understanding electron configuration is key to determining the chemical properties of transition elements. Electron configuration refers to the arrangement of electrons around the nucleus of an atom. In transition elements, this arrangement begins after the noble gas core. For instance, in the first transition series, we start with Scandium (Sc) which has the configuration \([\text{Ar}] \, 3d^1 \, 4s^2\). Each subsequent element in the series adds one more electron primarily to the 3d subshell. This is why Vanadium (V) is \([\text{Ar}] \, 3d^3 \, 4s^2\), and Chromium (Cr) interestingly becomes \([\text{Ar}] \, 3d^5 \, 4s^1\), showing a deviation due to stability preferences, as having half-filled or fully filled orbitals lends additional stability.

• Examples of electron configurations: Iron (Fe), \([\text{Ar}] \, 3d^6 \, 4s^2\) and Copper (Cu), \([\text{Ar}] \, 3d^{10} \, 4s^1\).
• This pattern demonstrates how electrons fill the d-orbitals, significantly impacting the chemical behavior of these elements.

Diamagnetic Elements

Diamagnetism arises in materials when all electrons are paired, resulting in no net magnetic moment. In our transition series, to find diamagnetic elements, we look for those with completely filled subshells. This relates closely to electron configurations, where fully paired electrons occur.
Zinc (Zn) with \([\text{Ar}] \, 3d^{10} \, 4s^2\) and Copper (Cu) with \([\text{Ar}] \, 3d^{10} \, 4s^1\) are excellent examples of diamagnetic materials. Their d-orbitals are completely filled with paired electrons, meaning they are not influenced by external magnetic fields and demonstrate weak repulsion to them.

• Cu and Zn are stable due to filled d-subshells, thus placing them in the category of diamagnetic elements.
• The lack of unpaired electrons implies no net magnetic moment.

Unpaired Electrons

The concept of unpaired electrons often determines how an element behaves magnetically. Unpaired electrons are those that do not have a corresponding electron with opposite spin in the same orbital, creating a net magnetic spin. In transition metals, these unpaired electrons primarily reside in the 3d subshell.
Manganese (Mn) with electron configuration \([\text{Ar}] \, 3d^5 \, 4s^2\) has the highest number of unpaired electrons with five unpaired electrons in the 3d orbital. Unpaired electrons endow the element with ferromagnetic or paramagnetic properties, meaning it can be attracted to a magnetic field or retain magnetization.

• These unpaired electrons make Mn more magnetic compared to other elements in the series.
• The presence of unpaired electrons influences the reactivity and potential for forming chemical bonds.