Problem 3 - Chemistry and Chemical Reactivity

Question

Identify an ion of a first series transition metal that is isoelectronic with each of the following. (a) \(\mathrm{Fe}^{3+}\) (b) \(\mathrm{Zn}^{2+}\) (c) \(\mathrm{Fe}^{2+}\) (d) \(\mathrm{Cr}^{3+}\)

Step-by-Step Solution

Answer

(a) \(\mathrm{V}^{2+}\), (b) \(\mathrm{Ni}^{+}\), (c) \(\mathrm{Mn}^{3+}\), (d) \(\mathrm{V}^{+}\).

Step 1: Understanding the Problem

To find ions that are isoelectronic with given ions, we must find ions that have the same number of electrons. Isoelectronic means having the same electronic configuration.

Step 2: Determine the Electron Configuration of Each Ion

First, determine the number of electrons each given ion has. Then identify the electron configuration for each.

Step 3: Find the Electron Configuration of Each Ion (a-d)

- (a) For \(\mathrm{Fe}^{3+}\), the atomic number of Fe is 26, so it has 26 protons and hence 26 electrons.When it loses 3 electrons to become \(\mathrm{Fe}^{3+}\), it has 23 electrons.Therefore, its configuration is \(1s^2 \,2s^2 \,2p^6 \,3s^2 \,3p^6 \,3d^5\).(b) \(\mathrm{Zn}^{2+}\) loses 2 electrons to achieve Zn configuration of \(\mathrm{Ar}\,3d^{10}\), having 28 electrons.(c) \(\mathrm{Fe}^{2+}\): Fe loses 2 electrons to become \(\mathrm{Fe}^{2+}\), so it has 24 electrons with configuration \(\mathrm{Ar}\,3d^{6}\).(d) \(\mathrm{Cr}^{3+}\): \(\mathrm{Cr}\) (Z=24) loses 3 electrons, it has 21 electrons, and configuration \(\mathrm{Ar}\,3d^{3}\).

Step 4: Finding Isoelectronic Ions

Now, we need to find ions from other first series transition metals that match these electron configurations.

Step 5: Find Isoelectronic Ion for (a)

As \(\mathrm{Fe}^{3+}\) has 23 electrons, \(\mathrm{Ti}^{+}\) (24 - 1 = 23) or \(\mathrm{V}^{2+}\) (23) could also be possible options.

Step 6: Find Isoelectronic Ion for (b)

As \(\mathrm{Zn}^{2+}\) has 28 electrons, \(\mathrm{Ni}^{+}\) with its 28 electrons is isoelectronic.

Step 7: Find Isoelectronic Ion for (c)

As \(\mathrm{Fe}^{2+}\) has 24 electrons, \(\mathrm{Mn}^{3+}\) with its 24 electrons is isoelectronic.

Step 8: Find Isoelectronic Ion for (d)

As \(\mathrm{Cr}^{3+}\) has 21 electrons, \(\mathrm{Ca}^{2+}\) (20 + 1 = 21 when it loses 2 electrons) or \(\mathrm{V}^{+}\), having 21 electrons, are isoelectronic options.

Key Concepts

Isoelectronic Species

Isoelectronic species are fascinating as they have identical numbers of electrons and thus the same electron configuration, even if they are not the same chemical species. This concept can be best understood by breaking it down into clear steps:

• Count the total number of electrons for both the given ion and the candidate ions.
• Compare their electron configurations to ensure they match exactly.

When ions possess equal numbers of electrons, their configurations align, simplifying the understanding of bonding and reactivity. This concept is especially important in chemistry as it helps identify species with similar chemical properties, even when they differ in atomic or molecular identities. By understanding isoelectronic species, you can make predictions about chemical behavior and interactions.

Electron Configuration

Electron configuration describes the arrangement of electrons in an atom or ion. To understand this arrangement, think of electron configurations as a map of where electrons are located around the nucleus:

• Electrons fill orbitals following the "Aufbau principle"—starting filling from the lowest energy level.
• The order is typically expressed as following: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, etc.
• For ions, electrons are removed from the outermost shell, typically from the s or p orbitals first.

Each orbital can hold a specific number of electrons: 2 for the s orbital, 6 for the p orbital, 10 for the d orbital, and 14 for the f orbital. Understanding electron configuration bridges our knowledge between atomic structure and an elemental behavior.

First Series Transition Metals

Transition metals in the first series consist of elements from Scandium (Sc) to Zinc (Zn). These elements are unique due to their partially filled d subshells, which provide a wealth of chemical and physical properties:

• Typically, they have variable oxidation states.
• They are often good conductors of electricity.
• They engage in complex ion formation.

The partially filled d orbitals allow transition metals to form colored compounds and exhibit magnetic properties. This is why they are often used in various industrial applications including catalysts and materials science. Transition metals' versatility comes from the fact that their electrons can freely move among the d orbitals, allowing complex and varied chemical behaviors.

Chemical Bonding

Chemical bonding involves the interaction of electron clouds between atoms to form compounds. Various types of bonding exist, and each has unique attributes:

• Ionic Bonding: Occurs when electrons are transferred from one atom to another, resulting in oppositely charged ions attracting each other.
• Covalent Bonding: Involves the sharing of electron pairs between atoms. These can further be classified as polar or nonpolar.
• Metallic Bonding: Found in metals where electrons flow freely among the cations, forming a 'sea' of electrons.

Transition metals often participate in metallic bonding, especially within alloys. Understanding these bonds aids in predicting how substances will interact, their reactivity, and their properties. This is crucial in designing new materials with desired characteristics for technological and industrial use.