Problem 31 - Chemistry The Central Science

Question

(a) What is an isoelectronic series? (b) Which neutral atom is isoelectronic with each of the following ions: \(\mathrm{Ga}^{3+}, \mathrm{Zr}^{4+}\) \(\mathrm{Mn}^{7+}, \Gamma, \mathrm{Pb}^{2+} ?\)

Step-by-Step Solution

Answer

(a) An isoelectronic series is a group of ions or atoms that share the same number of electrons but may have different charges and atomic numbers. (b) The neutral atoms isoelectronic with the given ions are: \(\mathrm{Ga}^{3+}\) - Nickel (Ni), \(\mathrm{Zr}^{4+}\) - Krypton (Kr), \(\mathrm{Mn}^{7+}\) - Argon (Ar), and \(\mathrm{Pb}^{2+}\) - Mercury (Hg).

Step 1: Understand an isoelectronic series

An isoelectronic series is a group of ions or atoms that share the same number of electrons but may have different charges and atomic numbers.

Step 2: Calculate the number of electrons in each ion

1. For \(\mathrm{Ga}^{3+}\): The atomic number of Gallium (Ga) is 31. Since it has a charge of +3, it has lost 3 electrons. Therefore, the number of electrons in this ion is \(31-3=28\). 2. For \(\mathrm{Zr}^{4+}\): The atomic number of Zirconium (Zr) is 40. Since it has a charge of +4, it has lost 4 electrons. Therefore, the number of electrons in this ion is \(40-4=36\). 3. For \(\mathrm{Mn}^{7+}\): The atomic number of Manganese (Mn) is 25. Since it has a charge of +7, it has lost 7 electrons. Therefore, the number of electrons in this ion is \(25-7=18\). 4. For \(\mathrm{Pb}^{2+}\): The atomic number of Lead (Pb) is 82. Since it has a charge of +2, it has lost 2 electrons. Therefore, the number of electrons in this ion is \(82-2=80\).

Step 3: Find the neutral atoms with the calculated electrons

1. For 28 electrons, the neutral atom is Nickel (Ni), which has an atomic number of 28. 2. For 36 electrons, the neutral atom is Krypton (Kr), which has an atomic number of 36. 3. For 18 electrons, the neutral atom is Argon (Ar), which has an atomic number of 18. 4. For 80 electrons, the neutral atom is Mercury (Hg), which has an atomic number of 80.

Step 4: List the isoelectronic neutral atoms

Isoelectronic neutral atoms for the given ions are as follows: - \(\mathrm{Ga}^{3+}\): Nickel (Ni) - \(\mathrm{Zr}^{4+}\): Krypton (Kr) - \(\mathrm{Mn}^{7+}\): Argon (Ar) - \(\mathrm{Pb}^{2+}\): Mercury (Hg)

Key Concepts

Electron Configuration

Electron configuration describes the arrangement of electrons in an atom's orbitals. Electrons are organized in shells and subshells based on the increasing energy levels. The configuration follows the Aufbau principle, where electrons fill lower energy levels before higher ones. For example, the electron configuration for a neutral argon (Ar) atom is \(1s^2 2s^2 2p^6 3s^2 3p^6\).
The goal of understanding electron configurations brings insight into how atoms will bond or interact with each other. It's crucial for predicting chemical behavior, as elements with similar configurations often have similar properties. For ions, electron configurations adjust based on the gain or loss of electrons. These changes can significantly alter the chemical properties, making it an important concept in chemistry.

Ions

Ions are atoms or molecules that have gained or lost electrons, resulting in a net positive or negative charge. When an atom loses electrons, it becomes a positively charged ion, known as a cation. Conversely, when an atom gains electrons, it becomes a negatively charged ion, known as an anion.
Positive ions occur, for example, when metals lose electrons. Conversely, non-metals often gain electrons to become anions. The charge of an ion equals the number of electrons lost or gained. For instance, \( ext{Ga}^{3+}\) has lost three electrons, leading to a 3+ charge. Understanding ions is critical for studying reactions in chemistry, like the formation of ionic compounds where cations and anions combine to achieve stable electron configurations.

Neutral Atoms

Neutral atoms are atoms with no overall charge. This balance occurs because they contain the same number of protons, positively charged particles, and electrons, negatively charged particles. The electron configuration of a neutral atom defines its chemical properties and reactivity.
Neutral atoms can become ions by losing or gaining electrons. However, in their neutral state, they reflect their pure elemental form. For example, a neutral Nickel (Ni) atom has 28 protons and 28 electrons, making it isoelectronic with \( ext{Ga}^{3+}\). Tracking how neutral atoms adjust into ions helps in predicting isoelectronic series, aiding in the understanding of periodic trends and atomic interactions.

Atomic Number

The atomic number is a unique identifier of an element that represents the number of protons found in the nucleus of a neutral atom. It also determines the element's position in the periodic table. For neutral atoms, it is equal to the number of electrons.
Changes in atomic number directly affect the element's identity. When calculating ionic forms, it remains consistent, while the number of electrons changes according to gained or lost particles. Recognizing elements by their atomic number simplifies the task of determining electron configurations and relating ions to their neutral atom counterparts. For instance, the atomic number of Argon (Ar) is 18, indicating its position and electron count.