Question

Write the ground-state electron configurations of the following ions, which play important roles in biochemical processes in our bodies: (a) \(\mathrm{Na}^{+},\) (b) \(\mathrm{Mg}^{2+}\), (c) \(\mathrm{Cl}^{-}\) (d) \(\mathrm{K}^{+}\) (e) \(\mathrm{Ca}^{2+}\) (f) \(\mathrm{Fe}^{2+},(\mathrm{g}) \mathrm{Cu}^{2+}\) (h) \(\mathrm{Zn}^{2+}\)

Short answer

(a) \(1s^2 2s^2 2p^6\), (b) \(1s^2 2s^2 2p^6\), (c) \(1s^2 2s^2 2p^6 3s^2 3p^6\), (d) \(1s^2 2s^2 2p^6 3s^2 3p^6\), (e) \(1s^2 2s^2 2p^6 3s^2 3p^6\), (f) \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^6\), (g) \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^9\), (h) \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10}\).

Step-by-step solution

Understanding Ground-State Electron Configuration

In atoms, electrons are arranged around the nucleus according to their energy levels and sublevels, with each atom having a unique electron configuration. In ions, electron configurations are adjusted based on their charge: cations lose electrons and anions gain electrons. Thus, understanding whether the ion loses or gains electrons is crucial for determining its electron configuration.

Calculating Electron Configuration for Neutral Atoms

We start by determining the electron configurations of the neutral atoms before forming ions. Use the periodic table to find the atomic number, which indicates the total electrons in the neutral atom: - Na (Sodium): 11 electrons - Mg (Magnesium): 12 electrons - Cl (Chlorine): 17 electrons - K (Potassium): 19 electrons - Ca (Calcium): 20 electrons - Fe (Iron): 26 electrons - Cu (Copper): 29 electrons - Zn (Zinc): 30 electrons.

Adjusting for the Ion's Charge

Depending on whether the ion is an anion or cation, adjust the number of electrons. For cations ( - Na, Mg, K, Ca, Fe, Cu, Zn): Subtract electrons according to the positive charge. For anions ( - Cl): Add electrons according to the negative charge.

Writing Electron Configurations for Ions

Now write the electron configurations for each ion based on the total number of electrons for the ion:(a) For \( \mathrm{Na}^+ \): 11 electrons - 1 electron = 10 electrons, configuration: \( 1s^2 2s^2 2p^6 \).(b) For \( \mathrm{Mg}^{2+} \): 12 electrons - 2 electrons = 10 electrons, configuration: \( 1s^2 2s^2 2p^6 \).(c) For \( \mathrm{Cl}^- \): 17 electrons + 1 electron = 18 electrons, configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 \).(d) For \( \mathrm{K}^+ \): 19 electrons - 1 electron = 18 electrons, configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 \).(e) For \( \mathrm{Ca}^{2+} \): 20 electrons - 2 electrons = 18 electrons, configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 \).(f) For \( \mathrm{Fe}^{2+} \): 26 electrons - 2 electrons = 24 electrons, configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 \). (g) For \( \mathrm{Cu}^{2+} \): 29 electrons - 2 electrons = 27 electrons, configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 3d^9 \). (h) For \( \mathrm{Zn}^{2+} \): 30 electrons - 2 electrons = 28 electrons, configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} \).

Key concepts

Ground-State Electron Configuration

The ground-state electron configuration of an atom reflects the most stable arrangement of electrons around the nucleus. In their natural state, electrons fill orbitals following a specific order based on increasing energy, known as the Aufbau principle. The primary goal is to achieve the lowest possible energy level for the electrons. Electrons occupy the available sublevels in a typical sequence:

• Starting from the lowest energy (1s) and moving progressively to higher energy orbitals (2s, 2p, 3s, etc.).
• Each orbital can hold a maximum of two electrons with opposite spins.
• The distribution follows the Pauli Exclusion Principle and Hund's Rule, optimizing electron configuration stability.

Understanding ground-state electron configurations is essential when discussing ions, forms that atoms take when they lose or gain electrons to become more stable.

Ions in Biochemistry

Ions are fundamental in biochemical processes as they help in nerve transmission, muscle contraction, and maintaining the fluid balance within our bodies. Unlike neutral atoms, ions carry a charge due to gain or loss of electrons.In biochemistry:

• Ions such as sodium (\(\mathrm{Na}^{+}\)) and potassium (\(\mathrm{K}^{+}\)) facilitate electrical signaling in nerves and muscles.
• Calcium (\(\mathrm{Ca}^{2+}\)) is crucial for bone health and acts as a signaling molecule.
• Magnesium (\(\mathrm{Mg}^{2+}\)) plays a role in enzyme regulation and energy production.
• Chloride (\(\mathrm{Cl}^{-}\)) helps in regulating osmotic balance and pH levels.

Ions are often involved in maintaining biochemical home'stasis, emphasizing the necessity to comprehend their electron configurations for studying biological systems.

Electron Configuration of Ions

When an atom becomes an ion, its electron configuration changes due to the gain or loss of electrons. The electron configuration of ions is pivotal to understanding their chemical behavior. Here's how it happens:

• For cations (positively charged ions), electrons are removed from the neutral atom, usually starting with the outermost energy level.
• For anions (negatively charged ions), electrons are added, often filling the outer electron shell.
• The desired result is often that ions achieve a noble gas configuration, which is energetically favorable.

For instance, \(\mathrm{Na}^{+}\) and \(\mathrm{Cl}^{-}\) gain or lose electrons to resemble the electron configuration of neon, providing stability through electron shell completion.

Cations and Anions

Cations and anions are two types of ions, characterized by their positive and negative charges, respectively. The process of forming these ions involves:

• Cations form by losing electrons, resulting in a positive charge. These ions are formed by metals such as sodium (\(\mathrm{Na}^{+}\)), magnesium (\(\mathrm{Mg}^{2+}\)), and calcium (\(\mathrm{Ca}^{2+}\)), which typically achieve stability by surrendering their outer electrons.
• Anions are created by gaining electrons, resulting in a negative charge. Nonmetals like chlorine turn into chloride (\(\mathrm{Cl}^{-}\)), achieving a full valence shell like the noble gases.

Understanding how these charges form is crucial in predicting chemical reactivity and properties, as these electrically charged particles are central to forming ionic compounds.

Transition Metals Electron Configuration

Transition metals exhibit unique behaviors regarding electron configurations, particularly as ions.Distinctively, they can form stable structures by losing various numbers of d-electrons:

• These metals often exhibit multiple oxidation states because they can lend electrons from their outer s and inner d orbitals.
• For instance, \(\mathrm{Fe}^{2+}\) results from iron losing two 4s electrons, while further oxidation can involve losing d electrons.
• Copper (\(\mathrm{Cu}^{2+}\)) typically loses its 4s electron before the d-electrons, illustrating typical transition metal behavior.

Furthermore, the electron configurations influence their catalytic abilities and unique magnetic properties, making understanding their electron behavior critical in industrial and technological applications.