Question

Refer to the periodic table and state the noble gas with an electron configuration identical to each of the following ions: (a) \(S^{2-}\) (b) \(\mathrm{Cl}^{-}\) (c) \(\mathrm{K}^{+}\) (d) \(\mathrm{Ca}^{2+}\)

Short answer

All ions have an electron configuration like Argon, \([\text{Ar}]\).

Step-by-step solution

Understand the electron configuration concept

Electron configuration represents the distribution of electrons in an atom or ion. For ions, we add electrons for anions and remove electrons for cations.

Determine the original electron configuration

Identify the neutral atom corresponding to each given ion and its electron configuration based on the periodic table.- For Sulfur (S), atomic number 16, configuration is: \([\text{Ne}] \, 3s^2 \, 3p^4\)- For Chlorine (Cl), atomic number 17, configuration is: \([\text{Ne}] \, 3s^2 \, 3p^5\)- For Potassium (K), atomic number 19, configuration is: \([\text{Ar}] \, 4s^1\)- For Calcium (Ca), atomic number 20, configuration is: \([\text{Ar}] \, 4s^2\)

Adjust for the ion electron count

Adjust the electron configuration based on the gain or loss of electrons to form each ion.- For \(S^{2-}\): Add 2 electrons to sulfur's configuration: \([\text{Ne}] \, 3s^2 \, 3p^6\)- For \(\text{Cl}^{-}\): Add 1 electron to chlorine's configuration: \([\text{Ne}] \, 3s^2 \, 3p^6\)- For \(\text{K}^{+}\): Remove 1 electron from potassium's configuration: \([\text{Ar}]\)- For \(\text{Ca}^{2+}\): Remove 2 electrons from calcium's configuration: \([\text{Ar}]\)

Match with noble gas configuration

Compare the resulting electron configurations with those of noble gases to identify matching ones.- For \(S^{2-}\) and \(\text{Cl}^{-}\), both match \([\text{Ar}]\), the configuration of Argon.- For \(\text{K}^{+}\) and \(\text{Ca}^{2+}\), both configurations also match \([\text{Ar}]\), the configuration of Argon.

Key concepts

Ions

Ions are atoms or molecules that have gained or lost electrons, giving them a net charge. When an atom gains electrons, it becomes negatively charged and is called an anion. Conversely, when an atom loses electrons, it becomes positively charged and is called a cation. This process affects the atom's electron configuration. Understanding ions is crucial because they are involved in various chemical reactions and play essential roles in the formation of compounds.

• Cations: Formed by losing electrons; positive charge.
• Anions: Formed by gaining electrons; negative charge.

The stability of an ion often resembles that of the nearest noble gas, resulting in a similar electron configuration.

Noble Gases

Noble gases are a group of elements in the periodic table known for their inertness and stability. They have fully filled outer electron shells, which makes them highly stable and generally unreactive.

• Located in Group 18 of the periodic table.
• Includes elements like Helium, Neon, Argon, and others.

The electron configurations of noble gases are often reference points for other elements attempting to reach similar stability through chemical interactions. Many ions form to achieve an electron configuration similar to that of a noble gas, thus gaining stability.

Periodic Table

The periodic table is an organized chart of chemical elements arranged based on their atomic number, electron configurations, and recurring chemical properties. This powerful tool helps scientists understand element relationships and predicts chemical behavior.

• Groups: Vertical columns with elements sharing similar chemical properties.
• Periods: Horizontal rows with elements having the same number of electron shells.

Understanding the periodic table is vital for identifying how elements form ions and what their stable configurations look like compared to noble gases.

Anion

An anion is a negatively charged ion, formed when an atom or molecule gains one or more electrons. This additional electron(s) increases the negative charge. Here's how it happens: When a non-metal like chlorine gains an electron, it forms an anion \( \text{Cl}^- \), resulting in a stable electron configuration similar to Argon. Anions are essential components in various chemical processes, from salt formation to electrical conductivity in solutions.

• Common examples: \( \text{Cl}^-, \text{O}^{2-}, \text{S}^{2-} \).
• Anions typically form from nonmetals.

Overall, anions work to achieve a stable, noble gas-like electron configuration.

Cation

A cation is a positively charged ion, produced when an atom loses one or more electrons, thus carrying a net positive charge. Metals often lose electrons to become cations, achieving a stable configuration similar to the preceding noble gas. For instance, when potassium loses an electron, it forms a cation \( \text{K}^+ \), matching the configuration of Argon. Cations are widespread in nature and technology, being crucial for processes such as electrical conduction and biological functions.

• Common examples: \( \text{Na}^+, \text{Ca}^{2+}, \text{K}^+ \).
• Cations frequently form from metals.

By losing electrons, cations strive to reach the stable configuration of a noble gas.