Question

Write the electron configurations for the following ions, and determine which have noble-gas configurations: \((\mathbf{a})\mathrm{Co}^{2+}\) \((\mathbf{b})\mathrm{Sn}^{2+},(\mathbf{c}) \mathrm{Zr}^{4+},(\mathbf{d}) \mathrm{Ag}^{+},(\mathbf{e}) \mathrm{S}^{2-}.\)

Short answer

The electron configurations for the given ions are: a) \(Co^{2+}\): [\(\text{Ar}\)] 3d^7 b) \(Sn^{2+}\): [\(\text{Kr}\)] 4d^10 5s^2 c) \(Zr^{4+}\): [\(\text{Kr}\)] d) \(Ag^{+}\): [\(\text{Kr}\)] 4d^10 e) \(S^{2-}\): [\(\text{Ne}\)] 3s^2 3p^6 The ions with noble-gas configurations are \(Sn^{2+}\), \(Zr^{4+}\), and \(S^{2-}\).

Step-by-step solution

a) Electron Configuration of Co2+ (Cobalt)

Cobalt (Co) has an atomic number of 27. Its electron configuration is [\(\text{Ar}\)] 3d^7 4s^2. To turn Co into Co2+ ion, we need to remove 2 electrons. We will remove the 2 electrons from the higher energy level first, which is the 4s orbital. So, the electron configuration for Co2+ is [\(\text{Ar}\)] 3d^7.

b) Electron Configuration of Sn2+ (Tin)

Tin (Sn) has an atomic number of 50. Its electron configuration is [\(\text{Kr}\)] 4d^10 5s^2 5p^2. To turn Sn into Sn2+ ion, we need to remove 2 electrons. We will remove the 2 electrons from the higher energy level first, which is the 5p orbital. So, the electron configuration for Sn2+ is [\(\text{Kr}\)] 4d^10 5s^2.

c) Electron Configuration of Zr4+ (Zirconium)

Zirconium (Zr) has an atomic number of 40. Its electron configuration is [\(\text{Kr}\)] 4d^2 5s^2. To turn Zr into Zr4+ ion, we need to remove 4 electrons. We will remove the 2 electrons from the higher energy level first, which are in the 5s orbital. Next, remove 2 electrons from the 4d orbital. So, the electron configuration for Zr4+ is [\(\text{Kr}\)].

d) Electron Configuration of Ag+ (Silver)

Silver (Ag) has an atomic number of 47. Its electron configuration is [\(\text{Kr}\)] 4d^10 5s^1. To turn Ag into an Ag+ ion, we need to remove one electron. We will remove the electron from the higher energy level first, which is the 5s orbital. So, the electron configuration for Ag+ is [\(\text{Kr}\)] 4d^10.

e) Electron Configuration of S2- (Sulfide)

Sulfur (S) has an atomic number of 16. Its electron configuration is [\(\text{Ne}\)] 3s^2 3p^4. To turn S into an S2- ion, we need to add 2 electrons. We will add the 2 electrons to the 3p orbital. So, the electron configuration for S2- is [\(\text{Ne}\)] 3s^2 3p^6.

Noble-Gas Configurations

The ions with noble-gas configurations are: - Sn2+ with an electron configuration of [\(\text{Kr}\)] 4d^10 5s^2, which resembles the noble gas Kr. - Zr4+ with an electron configuration of [\(\text{Kr}\)], which matches the noble gas Kr. - S2- with an electron configuration of [\(\text{Ne}\)] 3s^2 3p^6, which resembles the noble gas Ar.

Key concepts

Noble-Gas Configuration

Noble-gas configurations hold great significance in chemistry. These configurations are important because they resemble the electron configuration of noble gases, known for their stability. Noble gases, such as Helium (He), Neon (Ne), and Argon (Ar), have full outer electron shells, making them highly resistant to chemical changes.
Electrons in atoms strive to achieve this stable state, often by losing, gaining, or sharing electrons to reach a noble-gas configuration. In our original exercise, the goal was to determine whether the ions formed through electron removal or addition achieved such configurations. For example, in the case of Sn2+, Zr4+, and S2-, the ion configurations turned out to resemble the stable structure of noble gases like Krypton or Neon.
Achieving a noble-gas configuration often signifies a lower energy state and makes the ion or atom less likely to react further. This principle helps in predicting how elements will interact in chemical reactions, making it an essential concept in understanding chemistry.

Ions

Ions are charged particles formed when atoms gain or lose electrons. This process leads to a surplus or deficit of electrons, causing the atom to carry a charge.

• When an atom loses electrons, it becomes a positively charged ion, or cation.
• Conversely, when an atom gains electrons, it becomes a negatively charged ion, or anion.

Understanding ions is crucial for predicting chemical behavior and reactivity.
The original exercise emphasized forming ions, such as Co2+, Sn2+, Zr4+, Ag+, and S2-, through electron removal or addition. These ions differ from their neutral atoms, having distinct properties and reactivities due to their charges.
It's also important to recognize that the formation of ions is driven by the attempt to achieve a stable electronic configuration, often resembling that of a noble gas. This electron stability is a critical driver, guiding atoms to gain or lose electrons and thus form ions.

Electron Removal

Electron removal, or the process of taking electrons from an atom, results in the formation of positive ions called cations. This can be observed in the original exercise when dealing with metals like Cobalt (Co), Tin (Sn), Zirconium (Zr), and Silver (Ag). In each of these ions:

• Electrons were removed from the outermost shells or the highest energy level orbitals.
• For example, the removal from 4s for Co2+ or the 5s and 4d orbitals for Zr4+.

This removal aligns with the principle that electrons will be taken from the outermost or highest energy orbitals first, as these are the least tightly bound to the nucleus.
The process of electron removal is highly influenced by the desire to achieve a stable, lower-energy state in the form of a noble-gas configuration, if possible. It often involves high energy input as electrons are tightly held by the nucleus due to the positive charge. Understanding electron removal is key to studying reactions involving metals and ion formation.

Electron Addition

Electron addition, the opposite of electron removal, involves an atom gaining extra electrons, leading to the formation of negatively charged ions, or anions. In the original exercise, sulfur (S) gained electrons to become the sulfide ion (S2-).

• This occurs by adding electrons to the outer orbitals, in sulfur's case, to the 3p orbital.
• Unlike electron removal, adding electrons fills empty or partially filled orbitals.

The driving force behind electron addition is often to achieve a noble-gas electron configuration, reaching a completely filled outer shell.
Anions like S2- are common in non-metals and play a significant role in forming ionic compounds. Electron addition increases repulsion between electrons but provides a more stable ionic state. By gaining electrons, an atom can achieve a reduction in overall energy, resulting in increased stability. Understanding this process is crucial for predicting the behavior of elements that form anions.