Problem 13 - Chemistry: The Central Science in SI Units, Global Edition

Question

For each of the following compounds, determine the electron configuration of the transition-metal ion. (a) CuO, (b) \(\mathrm{Cu}_{2} \mathrm{O}\) (c) \(\mathrm{V}_{2} \mathrm{O}_{5}\) (d) \(\mathrm{MnO}\).

Step-by-Step Solution

Answer

The electron configurations of the transition-metal ions in the given compounds are as follows: a) CuO: Cu\(^{2+}\) has an electron configuration of \([Ar] 3d^9\). b) \(\mathrm{Cu}_{2}\mathrm{O}\): Cu\(^{+}\) has an electron configuration of \([Ar] 3d^{10}\). c) \(\mathrm{V}_{2}\mathrm{O}_{5}\): V\(^{5+}\) has an electron configuration of \([Ar] 3d^0\). d) \(\mathrm{MnO}\): Mn\(^{2+}\) has an electron configuration of \([Ar] 3d^5\).

Step 1: Identify the transition-metal ion and its oxidation state

In this compound, the transition-metal ion is copper (Cu). Oxygen usually has an oxidation state of -2. Since there's only one Cu atom, its oxidation state must be +2 to balance the overall charge of the compound.

Step 2: Determine the electron configuration of Cu\(^{2+}\)

The electron configuration of a neutral Cu atom is \([Ar] 3d^{10} 4s^1\). Removing two electrons from the outer shell (4s) and one from the inner shell (3d) gives the electron configuration of Cu\(^{2+}\): \([Ar] 3d^9\). #b) \(\mathrm{Cu}_{2}\mathrm{O}\)#

Step 1: Identify the transition-metal ion and its oxidation state

In this compound, the transition-metal ion is still copper (Cu). Since there are two Cu atoms and one O atom, the overall oxidation state of the two Cu atoms must be +2 to balance the overall charge of the compound (since O has an oxidation state of -2). Therefore, each Cu atom will have an oxidation state of +1.

Step 2: Determine the electron configuration of Cu\(^{+}\)

The electron configuration of a neutral Cu atom is \([Ar] 3d^{10} 4s^1\). Removing one electron from the outer shell (4s) gives the electron configuration of Cu\(^{+}\): \([Ar] 3d^{10}\). #c) \(\mathrm{V}_{2}\mathrm{O}_{5}\)#

Step 1: Identify the transition-metal ion and its oxidation state

In this compound, the transition-metal ion is vanadium (V). Oxygen usually has an oxidation state of -2. Since there are five O atoms (each with an oxidation state of -2), the overall oxidation state of the two V atoms must be +10 (to balance the overall charge). Therefore, each V atom will have an oxidation state of +5.

Step 2: Determine the electron configuration of V\(^{5+}\)

The electron configuration of a neutral V atom is \([Ar] 3d^3 4s^2\). Removing both electrons from the outer shell (4s) and three from the inner shell (3d) gives the electron configuration of V\(^{5+}\): \([Ar] 3d^0\). #d) \(\mathrm{MnO}\)#

Step 1: Identify the transition-metal ion and its oxidation state

In this compound, the transition-metal ion is manganese (Mn). Oxygen usually has an oxidation state of -2. Since there's only one Mn atom, its oxidation state must be +2 to balance the overall charge of the compound.

Step 2: Determine the electron configuration of Mn\(^{2+}\)

The electron configuration of a neutral Mn atom is \([Ar] 3d^5 4s^2\). Removing both electrons from the outer shell (4s) gives the electron configuration of Mn\(^{2+}\): \([Ar] 3d^5\).

Key Concepts

Oxidation States

Oxidation states, often referred to as oxidation numbers, help us understand the distribution of electrons among the atoms in molecules. They are essential for determining how electrons are transferred in reactions, a key concept in redox chemistry. Oxidation states are assigned based on a set of rules:

• Pure elements have an oxidation state of zero.
• For ions composed of only one atom, the oxidation state is equal to the charge of the ion.
• Oxygen typically has an oxidation state of -2 in compounds.
• Hydrogen has an oxidation state of +1 when bonded to non-metals.
• The sum of oxidation states in a neutral molecule must be zero.

In transition metal compounds, determining the oxidation state involves assuming the typical oxidation states of other elements, like oxygen, and then deducing the metal’s state. This understanding allows chemists to predict the electron configuration of the metal ion, crucial for naming the compound and predicting its chemistry.

Copper Compounds

Copper forms two common oxidation states in compounds: +1 and +2. Copper oxide ( CuO ) and copper(I) oxide ( Cu_{2}O ) are two illustrative examples. Here’s a closer look:

• CuO: This compound features copper in the +2 oxidation state. The neutral copper atom has an electron configuration of [Ar] 3d^{10} 4s^1 . To form Cu^{2+} , it loses two electrons, leading to [Ar] 3d^9 .
• Cu_{2}O: In this compound, each copper atom is in the +1 oxidation state. Removal of one electron from 4s orbital results in the electron configuration of Cu^{+}: [Ar] 3d^{10} , highlighting the complete filling of 3d orbitals.

These compounds have distinctive properties because of their differing copper oxidation states, influencing both their reactivity and color.

Vanadium Compounds

Vanadium compounds vary widely in oxidation states, from -3 to +5, with the most common being +2, +3, +4, and +5. The compound V_{2}O_{5} demonstrates vanadium in its highest oxidation state, +5, characterized as follows:
- In V_{2}O_{5} , each vanadium atom assumes an oxidation state of +5 to neutralize the -10 charge from five oxygens.
- The electron configuration of a neutral vanadium atom is [Ar] 3d^3 4s^2 . Stripping five electrons to form V^{5+} leaves [Ar] 3d^0 , meaning no electrons occupy the 3d or 4s orbitals.
This electron arrangement impacts the compound’s properties, such as its ability to act as an oxidizing agent, a role often leveraged in catalysis and electrochemical applications.

Manganese Compounds

Manganese can adopt several oxidation states, most commonly from +2 to +7, each yielding distinct chemical behaviors. Consider MnO , wherein manganese is in the +2 state:

• Here, Mn counterbalances oxygen’s -2 charge.
• A neutral manganese atom bears the configuration [Ar] 3d^5 4s^2 . Upon forming Mn^{2+} , the 4s electrons are removed, resulting in [Ar] 3d^5 , with a high-spin configuration across five 3d orbitals.

This oxidation state is prevalent in aqueous solutions and has implications for the magnetic properties and reactivity of manganese compounds, making them a critical focal point in transition metal chemistry.