Problem 96 - Chemistry: The Central Science in SI Units, Global Edition

Question

Identify \(a+2\) cation that has the following ground state electron configurations: (a) \([\mathrm{Ne}]\) (b) \([\mathrm{Ar}] 3 d^{9}\) (c) \([\mathrm{Xe}] 4 f^{14} 5 d^{10} 6 s^{2}\)

Step-by-Step Solution

Answer

The \(a+2\) cations for each case are: (a) None (b) \(Cu^{2+}\) (c) \(Hg^{2+}\)

Step 1: Case (a) \([\mathrm{Ne}]\)

Refer to the periodic table and find the element with the electron configuration \([\mathrm{Ne}]\). In this case, Neon's electron configuration is the same as the ground state electron configuration in question. The electron configuration of neutral Neon (Ne) is \(1s^2 2s^2 2p^6\), which is also represented as \([\mathrm{Ne}]\). For an \(a+2\) cation state, we need to consider removing two electrons from the outermost shell. However, considering the full electron configuration of neon, there are no outer electrons for the \(a+2\) cation. Thus, there is no valid \(a+2\) cation for case (a).

Step 2: Case (b) \([\mathrm{Ar}] 3 d^{9}\)

First, let's find the element with the given ground state electron configuration. The electron configuration of neutral Argon (Ar) is \(1s^2 2s^2 2p^6 3s^2 3p^6\), which can be represented as \([\mathrm{Ar}]\). Now, consider adding the \(3d^9\) configuration to argon, making the electron configuration \([\mathrm{Ar}] 3d^9\). This results in the element, Copper (Cu) with a neutral electron configuration of \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^1\). For an \(a+2\) cation, we need to remove two electrons from the outermost shell. In this case, we will remove the 4s electrons and then remove 1 of the 3d electrons. Doing this, the electron configuration of the \(a+2\) cation for copper will be \([\mathrm{Ar}] 3d^{9}\). The \(a+2\) cation for case (b) is \(Cu^{2+}\).

Step 3: Case (c) \([\mathrm{Xe}] 4 f^{14} 5 d^{10} 6 s^{2}\)

First, let's find the element with the given ground state electron configuration. The electron configuration of neutral Xenon (Xe) is \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 4d^{10} 5s^2 5p^6\), which can be represented as \([\mathrm{Xe}]\). Now, consider adding the \(4f^{14}\), \(5d^{10}\), and \(6s^2\) configurations to xenon, making the electron configuration \([\mathrm{Xe}] 4f^{14} 5d^{10} 6s^2\). This results in the element, Mercury (Hg) with a neutral electron configuration of \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 4d^{10} 5s^2 5p^6 4f^{14} 5d^{10} 6s^2\). For an \(a+2\) cation, we need to remove two electrons from the outermost shell. In this case, we will remove the 6s electrons. Doing this, the electron configuration of the \(a+2\) cation for mercury will be \([\mathrm{Xe}] 4f^{14} 5d^{10}\). The \(a+2\) cation for case (c) is \(Hg^{2+}\).

Key Concepts

Electron Configuration

Electron configuration is a way we use to describe how electrons are arranged around the nucleus of an atom. It's like the seating arrangement for electrons in different energy levels or shells. Each element's electronic configuration tells us which orbitals the electrons are in and how many are in each. To write electron configurations, we use a notation that combines numbers and letters:

• The number indicates the principal energy level or shell (n=1, 2, 3, ...)
• The letter (s, p, d, f) describes the type of orbital
• A superscript number indicates the number of electrons in those orbitals

For example, the electron configuration of Hydrogen is written as "1s¹," because it has one electron in the "s" orbital of the first shell. Knowing the electron configuration helps us understand many properties of the element, like its reactivity and the kind of bonds it forms with other elements.

Periodic Table

The periodic table is like a map for elements, providing a wealth of information about them. It organizes elements based on their atomic number, electron configurations, and chemical properties. When we look at this table, we can see trends in behavior among elements. Elements are arranged in rows called periods and columns known as groups or families.

• Periods tell us how many electron shells an element has.
• Groups give clues about the number of valence electrons and chemical reactivity.

For instance, elements in the same group tend to exhibit similar chemical behavior because they have the same number of electrons in their outermost shell. Additionally, the position of an element in the periodic table helps predict its electron configuration, which in turn influences its bonding and interaction with other elements. This is an invaluable tool for chemists and is fundamental in understanding chemistry.

Ions

Ions are atoms or molecules that have gained or lost electrons and thus have a net charge. Atoms are neutral when they have an equal number of protons (positively charged) and electrons (negatively charged). When an atom loses or gains electrons, it becomes charged and is called an ion. There are two types of ions:

• Cations: Positively charged ions, formed by losing electrons (e.g., Na⁺).
• Anions: Negatively charged ions, formed by gaining electrons (e.g., Cl^-).

The process of forming ions is crucial in chemistry as it explains how elements react and form compounds. For example, when a metal atom like sodium loses an electron, it becomes a cation, Na⁺. Conversely, a non-metal like chlorine can gain an electron to become an anion, Cl^-. Such ionic bonds, formed from the attraction between oppositely charged ions, are fundamental to the structure of many compounds, including salts.