Question

By means of orbital diagrams, write electron configurations for the following transition element atom and ions: \((a) \mathrm{Ti} ;(\mathbf{b}) \mathrm{V}^{3+} ;(\mathrm{c}) \mathrm{Cr}^{2+} ;(\mathrm{d}) \mathrm{Mn}^{4+} ;(\mathrm{e}) \mathrm{Mn}^{2+} ;(\mathrm{f}) \mathrm{Fe}^{3+}\).

Short answer

The electron configurations using orbital diagrams for the given atoms and ions are: (a) Ti: [Ar] 4s^2 3d^2 (b) V3+: [Ar] 3d^2 (c) Cr2+: [Ar] 3d^4 (d) Mn4+: [Ar] 3d^3 (e) Mn2+: [Ar] 3d^5 (f) Fe3+: [Ar] 3d^3.

Step-by-step solution

Titanium (Ti)

The atomic number of Titanium is 22, so it has 22 electrons in the ground state. The electron configuration is: \( [Ar] 4s^2 3d^2 \)

Vanadium Ion (V3+)

The atomic number of Vanadium is 23. As it's V3+, this means 3 electrons are removed. First, the 2 electrons from the 4s orbital will be lost, and then 1 from the 3d orbital. Thus, the electron configuration becomes: \( [Ar] 3d^2 \)

Chromium Ion (Cr2+)

The atomic number of Chromium is 24, but Chromium is a special case where one electron from 4s orbital moves to 3d orbital to attain half-full stability. But, here we have Cr2+ so 2 electrons are removed from the 4s orbital (since ionization starts from the outermost shell). Thus, the configuration changes to: \( [Ar] 3d^4 \)

Manganese Ion (Mn4+)

The atomic number of Manganese is 25. As we have Mn4+, it means 4 electrons are removed. First, 2 electrons are removed from the 4s orbital. After that, the next 2 are removed from the 3d orbital. Hence, the configuration becomes: \( [Ar] 3d^3 \)

Manganese Ion (Mn2+)

As previously discussed for Mn4+, here we have Mn2+ so, it means 2 electrons are removed. Firstly, the 2 electrons removed will be from 4s orbital. Thus, the configuration converts to: \( [Ar] 3d^5 \)

Iron Ion (Fe3+)

The atomic number of Iron is 26. Now, for Fe3+, 3 electrons are removed. First the electrons from the 4s orbital are lost, followed by one from the 3d. So, the electron configuration is: \( [Ar] 3d^3 \)

Key concepts

Transition Elements

Transition elements are a unique and interesting group of elements within the periodic table. They are found in groups 3 to 12, nestled between the s-block and the p-block.
These elements are known for having partially filled d orbitals. This property gives them their characteristic behaviors and properties.

**Unique Characteristics of Transition Elements**
- Transition elements have high melting and boiling points.
- They often exhibit multiple oxidation states, making them quite versatile in chemical reactions.
- These elements are typically very good conductors of electricity and heat.
- Many transition metals can form colored compounds, which makes them useful in dyes and pigments.

Understanding these characteristics helps us determine their electron configurations and predict how they might behave in chemical reactions.
In relation to our exercise, recognizing that transition elements include Ti, V, Cr, Mn, and Fe provides a basis for how to begin assessing their electron arrangements.

Orbital Diagrams

An orbital diagram is a way to visually represent the electron configuration of an atom. It shows each individual orbital as a box and fills them with electrons, which are represented by arrows.
When constructing orbital diagrams for atoms or ions, especially transition elements, it's vital to understand the energy levels: 4s is actually filled before 3d, though it is often written after it.

**Key Points on Orbital Diagrams**:

• Electrons are filled starting from the lowest energy level upward, according to the Aufbau principle.
• Each orbital can hold a maximum of two electrons, which must have opposite spins (represented by an up arrow and a down arrow in the diagram).
• Hund's rule suggests that electrons will fill empty orbitals within a sublevel before pairing up.

In the context of the exercise, for titanium (Ti) with atomic number 22, the electron configuration is \([Ar] 4s^2 3d^2\). This is depicted as two arrows in the 4s box and two arrows in the 3d box, reflecting the electrons' distribution.

Ionization

Ionization is the process of removing electrons from an atom or molecule, resulting in the formation of an ion. This process is crucial in forming cations (positively charged ions).
In transition metals, ionization commonly affects electrons in the outermost s orbital first, followed by the d orbitals. This is owing to the energy considerations where the 4s electrons are ionized before 3d electrons despite their filling order.

**Key Aspects of Ionization in Transition Elements**:

• Ionization energy, or the energy required to remove an electron, varies between elements. It typically increases across a period and decreases down a group.
• Transition metals often form cations with different charges; for example, iron can form \( ext{Fe}^{2+}\) and \( ext{Fe}^{3+}\) ions, which affects their chemical properties and reactivity.

In our exercise, ionization leads to changes in electron configurations, like for the vanadium ion \( ext{V}^{3+} \), reducing the electron count from 23 to 20, altering the configuration to \( [Ar] 3d^2 \). The ionization process plays a critical role in determining the chemical behavior of these transition elements in ionized states.