Question

Which noble gas is isoelectronic with each of the following nonmetal ions? (a) \(\mathrm{Cl}^{-}\) (b) I- (c) \(S^{2}\) (d) \(P^{3-}\)

Short answer

(a) Argon (Ar), (b) Xenon (Xe), (c) Argon (Ar), (d) Argon (Ar)

Step-by-step solution

Understanding Isoelectronic Species

Isoelectronic species are atoms, molecules or ions that have the same number of electrons. Noble gases generally have a full outer shell, so they are often isoelectronic with ions of other elements that have gained or lost electrons to achieve a full outer shell.

Determining Electron Count for \\( \mathrm{Cl}^- \\\)

A neutral chlorine atom has 17 electrons. By gaining one electron, the \( \mathrm{Cl}^- \) ion has 18 electrons. We need to identify the noble gas with 18 electrons, which is Argon (Ar).

Determining Electron Count for Iodine Ion (I-)

A neutral iodine atom has 53 electrons. By gaining one electron, the I- ion has 54 electrons. We need to identify the noble gas with 54 electrons, which is Xenon (Xe).

Determining Electron Count for \\( S^{2-} \\\)

A neutral sulfur atom has 16 electrons. By gaining two electrons, the \( S^{2-} \) ion has 18 electrons. Just like \( \mathrm{Cl}^- \), it is isoelectronic with Argon (Ar).

Determining Electron Count for \\( P^{3-} \\\)

A neutral phosphorus atom has 15 electrons. By gaining three electrons, the \( P^{3-} \) ion has 18 electrons. It is also isoelectronic with Argon (Ar).

Key concepts

Isoelectronic Species

Isoelectronic species refer to different atoms, ions, or molecules that have the same number of electrons. This means they often share similar electronic structures. A great way to understand this concept is to look at how nonmetals form isoelectronic relationships with noble gases. Nonmetals often gain electrons to achieve a stable electron configuration, resembling the nearest noble gas, which already has a full valence shell.

For example, the chloride ion \( \mathrm{Cl}^- \) adds one electron to its neutral form, resulting in 18 electrons, which makes it isoelectronic with Argon \((\mathrm{Ar})\). Understanding this concept helps in predicting the behavior of elements, as these species share common properties due to their identical electron configurations.

Electron Configuration

An element's electron configuration provides insight into how its electrons are distributed in atomic orbitals. Typically, electrons fill these orbitals in a specific order, from lower to higher energy levels. The electron configuration can predict an element's chemical behavior and its position in the periodic table.

For example, chlorine in its neutral state has an electron configuration of \([\mathrm{Ne}] 3s^2 3p^5\). When it gains an electron to become \( \mathrm{Cl}^- \), its configuration becomes \([\mathrm{Ne}] 3s^2 3p^6\), identical to that of Argon.

• This means \( \mathrm{Cl}^- \) has a full outer shell and is stable.
• Similarly, nonmetals achieve noble gas configurations through electron gain.
• Nonmetals like \(\mathrm{I}^-\), \(\mathrm{S}^{2-}\), and \(\mathrm{P}^{3-}\) follow the same principle, achieving the configurations of \(\mathrm{Xe}\), \(\mathrm{Ar}\), and \(\mathrm{Ar}\) respectively.

Nonmetal Ions

Nonmetals are elements that tend to gain electrons during chemical reactions, forming negatively charged ions, known as anions. This behavior is primarily due to their belief in attaining a stable electron configuration that resembles that of a noble gas, which provides them with a full outer electron shell.

For instance, sulfur \( \mathrm{S} \) becomes \( \mathrm{S}^{2-} \) by gaining two electrons to match the electron configuration of Argon. Similarly, iodine \( \mathrm{I} \) becomes \( \mathrm{I}^- \) by gaining an electron to match Xenon's stable configuration.

• Nonmetal ions are crucial in forming ionic compounds, as they readily combine with metal cations.
• They often exhibit distinct properties such as high electronegativity and ability to form various bonds.

Periodic Table Elements

The periodic table arranges elements according to their atomic number and properties, which helps predict their chemical behavior. Elements are grouped into periods and groups, providing a blueprint of their tendencies and reactivities.

Noble gases, located in Group 18, are unique as they exhibit a full valence shell, making them inert under standard conditions. Nonmetals often strive to share these stable attributes through electron gain.

• For example, chlorine, iodine, sulfur, and phosphorus all lie in specific spots, allowing predictions about their chemical tendencies.
• This arrangement is crucial for understanding why nonmetals form anions to become isoelectronic with neighboring noble gases.