Problem 5 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The maximum number of possible oxidation states of actinoides are shown by: (a) Nobelium (No) and lawrencium (Lr) (b) Actinium (Ac) and thorium (Th) (c) Berkelium (Bk) and californium (Cf) (d) Neptunium (Np) and plutonium (Pu)

Step-by-Step Solution

Answer

The answer is (d) Neptunium (Np) and Plutonium (Pu).

Step 1: Understand the Problem

The question asks us to identify the actinides that exhibit the maximum number of possible oxidation states. Actinides are elements found in the actinide series, and key examples are those that have multiple oxidation states due to their electron configurations.

Step 2: List Known Oxidation States

Review the common oxidation states for the actinides mentioned in the options: - Nobelium (No) typically shows +2 and +3 states. - Lawrencium (Lr) typically shows a +3 state. - Actinium (Ac) shows a +3 state. - Thorium (Th) shows +4 state predominantly. - Berkelium (Bk) shows +3 and +4 states. - Californium (Cf) shows +3 and +4 states. - Neptunium (Np) exhibits +3, +4, +5, +6, and +7 states. - Plutonium (Pu) exhibits +3, +4, +5, and +6 states.

Step 3: Compare the Possible Oxidation States

Compare the oxidation states from Step 2. Neptunium (Np) has the widest array of oxidation states ranging from +3 to +7. Plutonium (Pu) also has multiple states but fewer than neptunium. Both have more variety compared to the others.

Step 4: Select the Correct Answer

Based on Step 3 observations, Neptunium (Np) and Plutonium (Pu) show the maximum number of oxidation states compared to other options.

Key Concepts

Oxidation states

Oxidation states are like different sets of clothes an element can wear, depending on how it interacts with other elements. They tell us how many electrons an atom loses, gains, or shares when it forms chemical bonds. In simple terms, the oxidation state is a number that represents an atom's degree of oxidation. Actinides, which are elements with atomic numbers from 89 to 103, can have multiple oxidation states. This flexibility is mainly due to their electron configurations. Many actinides, like neptunium and plutonium, can exhibit a wide range of oxidation states, enabling them to form various compounds. For example:

• Neptunium (Np) has oxidation states from +3 to +7.
• Plutonium (Pu) typically displays +3, +4, +5, and +6 states.

Understanding these states is important in fields like nuclear chemistry since the chemical behavior of these elements changes with their oxidation states.

Neptunium

Neptunium (Np) is an intriguing element with several unique characteristics. It's the first transuranic element, meaning it comes right after uranium on the periodic table.

• Neptunium can have oxidation states of +3, +4, +5, +6, and even as high as +7.
• This wide range makes neptunium quite versatile in chemical reactions.

The ability of neptunium to adopt these different states allows it to participate in a variety of chemical processes. For instance, its +5 state is often encountered in aqueous solutions, exhibiting a green color. This variability in oxidation states makes it an element of interest in nuclear research and for potential use in nuclear reactors.

Plutonium

Plutonium (Pu) is another fascinating actinide, renowned for its use in nuclear power and weapons. It has a rich chemistry due to its multiple oxidation states, making it very reactive.

• Plutonium commonly exhibits oxidation states of +3, +4, +5, and +6.
• In each state, plutonium forms different types of compounds, influencing its reactivity and interactions.

When plutonium is in the +4 state, it is known as plutonium dioxide (PuO₂), which is an important starting material for many plutonium-based materials. Like neptunium, its behavior changes with oxidation states, which is crucial in understanding plutonium's behavior in nuclear applications.

Electron configurations

Electron configurations describe the arrangement of electrons in an element's atom. For the actinides like neptunium and plutonium, the electron configuration plays a significant role in their chemical properties.

• Actinides have electrons filling the 5f orbitals, which are more complex than the simpler s, p, or d orbitals.
• This complex filling leads to multiple possible oxidation states.

Understanding the electron configuration helps predict how an element will react chemically. For instance, as electrons fill higher energy 5f orbitals, actinides show increased variability in chemical reactions. This is why studying electron configurations is crucial for predicting and explaining the behavior of elements like neptunium and plutonium in different oxidation states.