Question

Which one of the following pairs of ions have the same electronic configuration? (a) \(\mathrm{Sr}^{3+}, \mathrm{Cr}^{3+}\) (b) \(\mathrm{Fe}^{3+}, \mathrm{Mn}^{2+}\) (c) \(\mathrm{Fe}^{3+}, \mathrm{Co}^{3+}\) (d) \(\mathrm{Cr}^{3+}, \mathrm{Fe}^{3+}\)

Short answer

(b) Fe^{3+}, Mn^{2+} have the same electronic configuration.

Step-by-step solution

Understand Electronic Configuration

Electronic configuration refers to the distribution of electrons of an atom or ion in its atomic or ion shells and subshells. To have the same electronic configuration, two ions must have the same number of electrons.

Calculate Electrons for Each Ion

Let's determine the number of electrons for each of the ions:- **Sr**: Atomic number is 38, - \(\text{Sr}^{3+}: 38 - 3 = 35 \text{ electrons}\)- **Cr**: Atomic number is 24, - \(\text{Cr}^{3+}: 24 - 3 = 21 \text{ electrons}\)- **Fe**: Atomic number is 26, - \(\text{Fe}^{3+}: 26 - 3 = 23 \text{ electrons}\)- **Mn**: Atomic number is 25, - \(\text{Mn}^{2+}: 25 - 2 = 23 \text{ electrons}\)- **Co**: Atomic number is 27, - \(\text{Co}^{3+}: 27 - 3 = 24 \text{ electrons}\)

Compare the Number of Electrons

Now, let's compare the calculated electrons for each ion: - Option (a): Sr^{3+} has 35 electrons, Cr^{3+} has 21 electrons. - Option (b): Fe^{3+} has 23 electrons, Mn^{2+} has 23 electrons. - Option (c): Fe^{3+} has 23 electrons, Co^{3+} has 24 electrons. - Option (d): Cr^{3+} has 21 electrons, Fe^{3+} has 23 electrons. From this, we observe that **Fe^{3+}** and **Mn^{2+}** both have 23 electrons.

Conclusion

The pair that has the same number of electrons, and therefore the same electronic configuration, is Fe^{3+} (23 electrons) and Mn^{2+} (23 electrons). This corresponds to option (b).

Key concepts

Understanding Ions

Ions are vital components in chemistry, essential for forming compounds and contributing to the behavior of chemical reactions. An ion is an atom or group of atoms with a net electric charge due to the loss or gain of one or more electrons. When an atom loses electrons, it forms a positively charged ion known as a cation. Conversely, when an atom gains electrons, it becomes a negatively charged ion or anion.

Let's break down this concept further:

• Cations: These are positively charged ions. They form when an atom loses electrons, resulting in fewer electrons than protons. For example, \( \text{Fe}^{3+} \) is a cation resulting from iron losing three electrons.
• Anions: These are negatively charged ions. They occur when an atom gains extra electrons, leading to more electrons than protons.
• Ionic Charge: The charge of an ion is determined by the difference between the number of protons and electrons.
  

Understanding ions helps explain how different substances interact and bond with each other in various chemical processes.

Exploring Electron Distribution

Electron distribution in an atom or ion determines its chemical properties and behaviors. This distribution, also known as the electronic configuration, defines how electrons are ordered into shells and subshells within an atom. The arrangement follows specific rules and principles: the Aufbau principle, Hund's Rule, and the Pauli exclusion principle.

Key points about electron distribution:

• Electron Shells: These are energy levels where electrons reside. The shell closest to the nucleus has the lowest energy.
• Subshells: Each shell contains one or more subshells (s, p, d, and f), each with a specific energy level and capacity for electrons.
• Filling Order: Electrons fill subshells in increasing energy order. The typical order is "1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s...".

When ions form, their electron distribution changes as they lose or gain electrons, leading them often to attain a configuration similar to noble gases, thus becoming more stable.

Diversity of Chemical Species

Chemical species refer to atoms, molecules, ions, or other specified forms of elements that have distinct chemical compositions and structures. The formation and interaction of chemical species are foundational to understanding chemical reactions and processes.

Here’s what you need to know about chemical species:

• Definition: A chemical species is a specific form of matter known or studied because of its identified chemical composition and structure. This can include single atoms, complex molecules, or charged ions.
• Stability: Different chemical species can have varying stability levels. Atoms often transform into different species to achieve more stable forms.
• Interactions: Chemical species are involved in forming bonds, participating in reactions, and undergoing transformations.
  

By recognizing different chemical species and their behaviors, students can better understand and predict the outcomes of chemical interactions and reactions.