Problem 111 - A Complete Resource Book in Chemistry for JEE Main

Question

The transition elements with some exceptions can show a large number of oxidation states. The various oxidation states are related to the electronic configuration of their atoms. The variable oxidation states of a transition metal is due to the involvement of \((\mathrm{n}-1) \mathrm{d}\) and outer \(\mathrm{ns}\)-electrons. For the first five elements of 3 d-transition series. The minimum oxidation state is equal to the number of electrons in 4s shell and the maximum oxidation state is equal to the sum of \(4 \mathrm{~s}\) and \(3 \mathrm{~d}\)-electrons. The relative stability of various oxidation state of a given element can be explained on the basis of stability of \(\mathrm{d}^{0}, \mathrm{~d}^{5}\) and \(\mathrm{d}^{10}\) configurations. In 3 d-series, the maximum oxidation state is shown by (a) \(\mathrm{Fe}(26)\) (b) Mn (atomic no.: 25 ) (c) \(\mathrm{Cr}(24)\) (d) Sc (atomic no: 21 )

Step-by-Step Solution

Answer

Manganese (Mn) shows the maximum oxidation state of +7.

Step 1: Understanding Oxidation States

Oxidation states refer to the degree of oxidation of an atom within a compound. For transition metals, these states are related to their electronic configuration, particularly the electrons in the \( (n-1)d \) and \( ns \) subshells.

Step 2: Minimum Oxidation State

The minimum oxidation state for each element in the 3d series is equal to the number of electrons in the 4s shell, which is typically +2. This is due to the fact that these are the first electrons to be removed.

Step 3: Maximum Oxidation State Calculation

The maximum oxidation state is determined by summing the 4s and the available 3d electrons. For a full d subshell, this results in a theoretical maximum of \( (n-1)d \) electrons plus \( ns \) electrons.

Step 4: Determining the Maximum Oxidation State of Given Options

For each transition metal: 1. **Scandium (Sc, atomic number 21)**: Electronic configuration \( [Ar] 3d^1 4s^2 \). Maximum oxidation state = 3.2. **Chromium (Cr, atomic number 24)**: Electronic configuration \( [Ar] 3d^5 4s^1 \). Maximum oxidation state = 6.3. **Manganese (Mn, atomic number 25)**: Electronic configuration \( [Ar] 3d^5 4s^2 \). Maximum oxidation state = 7.4. **Iron (Fe, atomic number 26)**: Electronic configuration \( [Ar] 3d^6 4s^2 \). Maximum oxidation state = 6.

Step 5: Conclusion

The element with the highest maximum oxidation state among the options is manganese (Mn) with a maximum oxidation state of +7, due to its \( 3d^5 4s^2 \) electron configuration.

Key Concepts

3d-transition series

The 3d-transition series is a fascinating group within the periodic table known for its unique properties and abilities to exhibit multiple oxidation states. Located in the d-block, these elements include Scandium (Sc) to Zinc (Zn). These ten elements, often referred to as the first transition series, have electrons filling the 3d subshell after the 4s subshell. What sets these elements apart is their partially filled d-orbitals. The partially filled d-orbitals allow them to have multiple possible oxidation states, which significantly influence their chemical behavior. In contrast to main group elements, which typically have a limited range of oxidation states, the 3d-transition metals can lose different numbers of d and s electrons to form cations with varying charges. This variability provides them a rich chemistry and makes them versatile in applications ranging from industrial catalysis to electronic devices. Students studying these metals will often explore how these elements exhibit unique magnetic and color properties, both of which are direct consequences of the arrangements and movements of d-electrons.

electronic configuration

Electronic configuration in transition metals is crucial to understanding their reactivity and oxidation states. In the 3d-transition series, electrons are added to the 3d subshell after filling the 4s subshell. This filling order - first 4s, then 3d - might seem counterintuitive at first, but it's due to the energy considerations involved. When you deconstruct any transition metal atom in this series, you find that the electrons are positioned in a specific order that minimizes energy while still allowing them to participate in bonding. For example, the electronic configuration of chromium (Cr) is \([Ar] 3d^5 4s^1\); this distinct arrangement contributes to its ability to achieve various oxidation states. The ordering of electrons results in each metal possessing distinctive chemical properties. Understanding these configurations not only provides insights into the element's basic character but also explains why they can gain and lose different numbers of electrons with relative ease. This ability of transition metals to have variable oxidation states enhances their usage in complex chemical reactions and industrial processes.

maximum oxidation state

The concept of the maximum oxidation state is integral to grasping the full potential of transition metals in chemical reactions. In these metals, the maximum oxidation state is determined by the total number of s and d electrons available for bonding. In the 3d-transition series, this typically means counting the electrons in both the 4s and 3d subshells. For instance, manganese (Mn) with an electronic configuration of \([Ar] 3d^5 4s^2\), can achieve a maximum oxidation state of +7. This happens because it can potentially lose all of its 3d and 4s electrons. This maximum oxidation potential is significant because it indicates the highest charge a metal can possess when combined with other elements. It influences the compound's stability and reactivity. Manganese's ability to reach an oxidation state of +7 makes it extremely versatile and valuable in various industrial and chemical processes, proving once again that understanding oxidation states is key to utilizing these metals efficiently.

oxidation state stability

Understanding the stability of oxidation states in transition metals can be complex due to their variable valencies, yet it's crucial for predicting the behavior of compounds they form. Stability arises when particular electron configurations are more energetically favorable. Within transition metals, electron configurations that lead to half-filled or completely filled d-orbitals are often more stable. Familiar examples are the \([d^5]\) and \([d^{10}]\) configurations. This is because these configurations offer a symmetrical electron distribution that minimizes repulsion, therefore providing extra stability. Stability considerations also explain differences like why Fe prefers +3 to +4 oxidation states. Electron scheme \([Ar] 3d^5 4s^0\) is more stable for Fe due to its half-filled d-band. These concepts highlight that although transition metals can exhibit a variety of oxidation states, not all are equally stable or likely to form. This insight is central to predicting and manipulating the chemical behavior of these fascinating elements in practical applications.