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

Question

In 3 d-series, the maximum oxidation state is shown by (a) \(\mathrm{Fe}(26)\) (b) Mn (atomic no. : 25 ) (c) \(\operatorname{Cr}(24)\) (d) Sc (atomic no: 21 )

Step-by-Step Solution

Answer

The maximum oxidation state in the 3d series is shown by Mn, which is +7.

Step 1: Understand the Oxidation States

The oxidation state of an element is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Transition metals can have multiple oxidation states due to the involvement of their d-orbitals.

Step 2: List Common Oxidation States in 3d Series

The common oxidation states for the 3d-series elements are as follows: Sc (21): +3, Ti (22): +4, V (23): +5, Cr (24): +6, Mn (25): +7, Fe (26): +6, Co (27): +3, Ni (28): +2, Cu (29): +2. Mn shows the highest oxidation state of +7.

Step 3: Identify Maximum Oxidation State

Among the given elements: Fe has a maximum oxidation state of +6, Mn can exhibit up to +7, Cr goes up to +6, and Sc is +3. Therefore, Mn has the highest possible oxidation state.

Key Concepts

Transition Metals

Transition metals are a group of elements found in the d-block of the periodic table. They typically include elements from groups 3 to 12. These metals are known for their ability to form a variety of different compounds. What makes transition metals special is their unique electron configurations, especially the filling of the d-orbitals. This allows them to exhibit multiple oxidation states, contributing to their vibrant colors and utility in forming catalysts. Some key characteristics of transition metals include their:

• Ability to form complex ions.
• Variable oxidation states.
• Formation of colored compounds.
• Paramagnetic properties.

These properties make transition metals versatile and widely used in various industries, ranging from chemical to material science applications.

Oxidation States

Oxidation states are a measure of the degree of oxidation or the number of electrons an atom can gain, lose, or share. For transition metals, the oxidation state can vary widely, which plays a crucial role in their chemistry. The versatility in oxidation states is primarily due to the energy difference between the s and d orbitals, allowing electrons to be lost or gained more readily. Understanding the oxidation state can help predict the types of compounds that a metal can form. For the 3d transition metals, common oxidation states can range widely, and familiarity with these states is essential for guessing what type of chemical reactions the metals might participate in. For example, manganese can exhibit oxidation states from +2 to +7. Knowing the typical oxidation states of transition metals helps in identifying their roles in both synthetic chemistry and biological systems.

d-Orbitals Involvement

The term 'd-orbitals' refers to the set of five orbitals that are found in the d-block elements. These orbitals can accommodate up to 10 electrons. What makes d-orbitals crucial is their role in bonding and the flexibility they offer for electron sharing. Unlike s and p orbitals, the d-orbitals have more complex shapes, enabling transition metals to form more diverse and complex structures. In transition metals, the electrons in these d-orbitals are involved in:

• Forming chemical bonds.
• Exhibiting multiple oxidation states.
• Contributing to the colored properties of compounds.

The involvement of d-orbitals in bonding is a reason why transition metals can lose varying numbers of electrons, resulting in multiple stable oxidation states. The participation of d-orbitals is also key to understanding the magnetic properties of these metals.

Maximum Oxidation State

Maximum oxidation state refers to the highest positive oxidation state an element can achieve in its compounds. For transition metals, this relates to their ability to lose their outer electrons in chemical reactions. The maximum oxidation state is determined by the extent of d-orbital participation along with electron configuration. For the 3d series transition metals:

• Manganese (Mn) shows the highest oxidation state at +7.
• Chromium (Cr) can achieve up to +6.
• Iron (Fe) reaches +6.
• Scandium (Sc) has a maximum oxidation state of +3.

Manganese reaching +7 showcases its full utilization of the available d-orbitals for bonding. Understanding these variations in oxidation states is important for predicting chemical behavior and reactivity. This property also allows transition metals to engage in diverse chemical environments, making them commercially valuable across different sectors.