Question

Write the expected electron configuration for (a) ${\mathrm{Cr}}^{3+}$, (b) ${\mathrm{Au}}^{3+},(\mathrm{c}){\mathrm{Ru}}^{2+}$ (d) ${\mathrm{Cu}}^{+}$, (e) ${\mathrm{Mn}}^{4+},(\mathrm{f}){\mathrm{Ir}}^{+}$

Short answer

(a) The electron configuration for Cr³⁺ is $[Ar]3d^4$. (b) The electron configuration for Au³⁺ is $[Xe]4f^{14}5d^9$. (c) The electron configuration for Ru²⁺ is $[Kr]4d^6$. (d) The electron configuration for Cu⁺ is $[Ar]3d^{10}$. (e) The electron configuration for Mn⁴⁺ is $[Ar]3d^3$. (f) The electron configuration for Ir⁺ is $[Xe]4f^{14}5d^{7}6s^1$.

Step-by-step solution

(a) Determine Electron Configuration for Cr³⁺)

First, we write the electron configuration for Cr, which has an atomic number of 24. This means the electron configuration is $[Ar]3d^{5}4s^1$. Since the charge is ³⁺, we remove 3 electrons from the outer subshells: 2 from the 4s and 1 from the 3d subshells. Thus, the electron configuration for Cr³⁺ is $[Ar]3d^4$.

(b) Determine Electron Configuration for Au³⁺)

Write the electron configuration for Au (gold, atomic number 79): $[Xe]4f^{14}5d^{10}6s^2$. Then, remove 3 electrons: 2 from the 6s, and 1 from the 5d. The electron configuration for Au³⁺ is $[Xe]4f^{14}5d^9$.

(c) Determine Electron Configuration for Ru²⁺)

Write the electron configuration for Ru (ruthenium, atomic number 44): $[Kr]4d^{7}5s^1$. Since the charge is ²⁺, remove 2 electrons: 1 from the 5s and 1 from the 4d. The electron configuration for Ru²⁺ is $[Kr]4d^6$.

(d) Determine Electron Configuration for Cu⁺)

Write the electron configuration for Cu (copper, atomic number 29): $[Ar]3d^{10}4s^1$. Removing 1 electron: from the 4s. The electron configuration for Cu⁺ is $[Ar]3d^{10}$.

(e) Determine Electron Configuration for Mn⁴⁺)

Write the electron configuration for Mn (manganese, atomic number 25): $[Ar]3d^{5}4s^2$. Since the charge is ⁴⁺, remove 4 electrons: 2 from the 4s and 2 from the 3d. The electron configuration for Mn⁴⁺ is $[Ar]3d^3$.

(f) Determine Electron Configuration for Ir⁺)

Write the electron configuration for Ir (iridium, atomic number 77): $[Xe]4f^{14}5d^{7}6s^2$. Removing 1 electron: from the 6s. The electron configuration for Ir⁺ is $[Xe]4f^{14}5d^{7}6s^1$.

Key concepts

Transition Metals

Transition metals are a group of metals found in the central block of the periodic table. These elements are known for their ability to form a wide range of oxidation states. This happens because they have partially filled d subshells. Here are some common characteristics of transition metals:

• High melting and boiling points.
• Good conductors of heat and electricity.
• Often form colored compounds.

These metals, when forming ions, usually lose electrons from their outermost energy levels. The d-orbitals in these elements are critical in defining their chemistry, contributing to their complex electron configurations and varied oxidation states. For instance, iron can exist in both ext{Fe}^{2+} and ext{Fe}^{3+} forms, maintaining the balance between stability and reactivity in complex reactions.
Transition metals often play a significant role in catalysis and are essential in bioinorganic chemistry due to the versatility of their oxidation states.

Oxidation States

Oxidation states refer to the degree of oxidation of an atom in a compound. It indicates the number of electrons lost or gained by an atom to form a bond. Transition metals are unique because they can exhibit multiple oxidation states.

• This is due to the similar energy levels of their 3d and 4s orbitals, allowing electrons to be removed more flexibly.
• A transition metal may lose different numbers of electrons depending on the chemical context, resulting in various oxidation states.

For instance, chromium can be found in +2, +3, and +6 oxidation states, showing its versatility in chemical reactions.
The oxidation state is crucial for understanding redox reactions where electrons are transferred between species. In cases where transition metals are involved, predicting the behavior of reactions requires a solid grasp of oxidation states.

Electron Removal Process

The electron removal process is critical to determining the electron configuration of ions, particularly for transition metals. When an atom becomes a cation (positively charged ion), it loses electrons.

• These electrons are removed first from the outermost energy level, or the shell with the highest n value, prioritizing s-orbitals before the d-orbitals.

For example, in creating ext{Cr}^{3+}, electrons are first removed from the 4s orbital rather than the 3d, even though 3d is filled before 4s in a neutral atom.
This is because electrons in the outer shell are higher in energy and are removed first. Understanding this process helps explain the formation of various oxidation states and the resulting chemical properties of the ions.

Atomic Structure

Atomic structure is the foundational concept that underlies the behavior of atoms, including electrons' arrangement around the nucleus. This structure is crucial for understanding chemical properties and reactions.

• Each atom consists of a nucleus (containing protons and neutrons) and electrons organized in energy levels or shells.
• These electrons occupy orbitals, specific regions with set energy levels determined by quantum mechanics.

For transition metals, the d-orbitals play a significant role, as they are involved in bonding and determining the physical and chemical properties of the metal. The specific filling and arrangement of these orbitals affect how these metals interact with other atoms.
In chemistry, atomic structure guides the prediction of molecular arrangements, properties, and behavior based on the periodic table and quantum theory.