Problem 82 - General Chemistry: Principles and Modern Applications

Question

All of the following elements have an ion displaying the +6 oxidation state except (a) Mo; (b) Cr; (c) Mn; (d) \(\mathrm{V} ;\) (e) S.

Step-by-Step Solution

Answer

The element which does not have an ion displaying the +6 oxidation state is (d) Vanadium (V).

Step 1: Understanding the Concept of Oxidation State

Firstly, understand that the oxidation state of an atom in a molecule refers to the degree of oxidation of that atom. It is defined as the charge that atom would have if all bonds were ionic. An atom can have an oxidation state ranging from -3 to +7, depending on its electron configuration and its position in the Periodic Table.

Step 2: Knowledge of Elements' Electron Configuration

Recognize that the highest possible oxidation state for an element is equal to the number of valence electrons that must be removed to form a cation. The position of the elements in the Periodic Table gives information about the valence electrons. Molybdenum (Mo) and Chromium (Cr) are in group 6 and can therefore display a +6 oxidation state. Manganese (Mn) is in group 7 and can lose up to 7 electrons, thus can also display a +6 oxidation state. Sulfur (S) being in group 16, also can display a +6 oxidation state.

Step 3: Finding the Element With a Different Maximum Oxidation State

Among the provided options, only Vanadium (V) is in group 5 of the Periodic Table, meaning that it has 5 valence electrons and can therefore only lose at most 5 electrons. Hence, it cannot display a +6 oxidation state.

Key Concepts

Electron Configuration

To understand the concept of electron configuration, you can think of it as an arrangement of electrons in an atom or ion. The electrons are arranged in shells or energy levels around the nucleus.

• The first shell, which is closest to the nucleus, can hold up to 2 electrons.
• The second shell can hold up to 8 electrons.
• Subsequent shells can hold even more, depending on the element's place in the periodic table.

The electron configuration determines how electrons in an atom are distributed among its orbitals. This configuration is significant because it dictates the chemical properties and reactivity of the element.For example, the electron configuration of Chromium (Cr) is \([Ar] 3d^5 4s^1\), which allows it to have different oxidation states, including a +6 oxidation state as in \( ext{CrO}_3\). Understanding the electron configuration helps in predicting how an element will bond with others and what oxidation states it can adopt.

Transition Metals

Transition metals are a group of elements found in the d-block of the periodic table, specifically from groups 3 to 12. These elements are characterized by having partially filled d orbitals.
Here are some important traits:

• They can exhibit multiple oxidation states because they have electrons that can be removed from both the s and d orbitals.
• They often form colored compounds.
• They can act as catalysts in chemical reactions.

The ability to take on multiple oxidation states is perhaps the most interesting feature of transition metals. This characteristic arises because the energy difference between the s and d orbitals is quite small. Manganese (Mn), for example, can display various oxidation states ranging from +2 to +7. Its flexibility in oxidation states allows it to participate in a multitude of different chemical reactions and processes.

Periodic Table Groups

Elements are organized in the periodic table into vertical columns known as groups. Each group has similar chemical and physical properties.

• Group 1 elements are known as alkali metals.
• Group 17 comprises the halogens, and Group 18 the noble gases.
• Transition metals are in the central block of the table, groups 3 through 12.

The group number gives significant insights into the valence electrons of the atom, which are the electrons available for bonding. For example, Molybdenum (Mo) and Chromium (Cr) are both in group 6, implying they can use these electrons to achieve high oxidation states like +6. Similarly, understanding the group placement can predict an element's typical behavior during chemical reactions and its likely compounds. Vanadium (V) in group 5 is limited to a +5 oxidation state due to its fewer valence electrons.