Problem 4 - Chemistry and Chemical Reactivity

Question

Give symbols and names for four monatomic ions that have the same electron configuration as argon.

Step-by-Step Solution

Answer

The ions are \(K^+\), \(Ca^{2+}\), \(Cl^-\), and \(S^{2-}\).

Step 1: Determine Argon's Electron Configuration

Argon is a noble gas with the atomic number 18. Its electron configuration is \([\text{Ne}]\,3s^2\,3p^6\). It is full in the outer shell, making it stable.

Step 2: Identify Possible Ion Charges

To have the same electron configuration as argon, other elements need to either lose or gain electrons to reach the total electron count of 18, similar to argon's configuration.

Step 3: Identify Cations and Calculate Electrons

Monatomic cations can achieve argon's electron configuration by losing electrons. Potassium (\(K^+\)) and calcium (\(Ca^{2+}\)) lose 1 and 2 electrons respectively, which reduces their electron count to 18.

Step 4: Identify Anions and Calculate Electrons

Monatomic anions can gain electrons to achieve argon's electron configuration. Chlorine (\(Cl^-\)) and sulfur (\(S^{2-}\)) gain 1 and 2 electrons respectively to reach an electron count of 18.

Step 5: List the Ions and Their Symbols

The ions that have the same electron configuration as argon are potassium ion \((K^+)\), calcium ion \((Ca^{2+})\), chloride ion \((Cl^-)\), and sulfide ion \((S^{2-})\). These ions have electron configurations equivalent to \([\text{Ne}]\,3s^2\,3p^6\).

Key Concepts

Electron Configuration

Electron configuration is a way to describe the distribution of electrons in an atom. It shows how electrons fill various energy levels around the nucleus.
For argon, a noble gas with an atomic number of 18, the electron configuration is \([\text{Ne}]\,3s^2\,3p^6\).This notation indicates that argon has its outer electron shell filled, with 8 electrons in the third shell (2 in the 3s subshell and 6 in the 3p subshell).

• Stability: This complete outer shell makes argon stable and unreactive.
• Understanding Configurations: Knowing an element's electron configuration helps predict chemical behavior and bonding.

Argon

Argon is a colorless, odorless noble gas found in the atmosphere. Its atomic number is 18, meaning it has 18 protons and usually 18 electrons.
Argon's complete outer shell of electrons makes it chemically inert.

• Noble Gas Characteristics: As a noble gas, argon is stable and reluctant to form chemical bonds.
• Real-World Use: Argon is widely used in lighting, welding, and preserving historical documents due to its non-reactive nature.

Noble Gases

Noble gases, including argon, are found in group 18 of the periodic table. They are characterized by a full outer shell of electrons, leading to high stability and low reactivity.

• Other Noble Gases: Helium, neon, krypton, xenon, and radon.
• Applications: Used in lighting solutions, such as neon lights and lasers, due to their inert properties.
• Importance in Chemistry: Noble gases serve as a standard for evaluating the electron configurations of other elements.

Ion Charges

Ions form when atoms lose or gain electrons to achieve a full outer shell, similar to noble gases like argon.
The charge of an ion represents the difference between the number of protons and electrons.

Cations and Anions

• Cations: Positively charged ions formed when atoms lose electrons. For example, potassium (\(K^+\)) and calcium (\(Ca^{2+}\)) become cations by losing 1 and 2 electrons, respectively, achieving the same electron configuration as argon.
• Anions: Negatively charged ions formed when atoms gain electrons. Chlorine (\(Cl^-\)) and sulfur (\(S^{2-}\)) gain 1 and 2 electrons, respectively, to match argon's electron configuration.
• Why It Matters: Understanding ion charges is crucial in predicting how elements combine to form compounds.