Question

Write the ground state electron configuration for (a) \(\mathrm{S}, \mathrm{S}^{2-}\) (b) \(\mathrm{Al}, \mathrm{Al}^{3+}\) (c) \(\mathrm{V}, \mathrm{V}^{4+}\) (d) \(\mathrm{Cu}^{+}, \mathrm{Cu}^{2+}\)

Short answer

Question: Provide the ground state electron configuration for the following elements and their ions: (a) S, S²⁻ (b) Al, Al³⁺ (c) V, V⁴⁺ (d) Cu⁺, Cu²⁺ Answer: (a) S: 1s²2s²2p⁶3s²3p⁴, S²⁻: 1s²2s²2p⁶3s²3p⁶ (b) Al: 1s²2s²2p⁶3s²3p¹, Al³⁺: 1s²2s²2p⁶ (c) V: 1s²2s²2p⁶3s²3p⁶4s²3d³, V⁴⁺: 1s²2s²2p⁶3s²3p⁶3d¹ (d) Cu⁺: 1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰, Cu²⁺: 1s²2s²2p⁶3s²3p⁶3d⁹

Step-by-step solution

Begin with given elements

For each part of the exercise, start by identifying the element or ion given. (a) S, S²⁻ (b) Al, Al³⁺ (c) V, V⁴⁺ (d) Cu⁺, Cu²⁺

Determine the number of electrons

Using the periodic table, find the atomic number (number of protons) for each element. Then, for ions, account for the gained or lost electrons. (a) S: 16 electrons, S²⁻: 18 electrons (b) Al: 13 electrons, Al³⁺: 10 electrons (c) V: 23 electrons, V⁴⁺: 19 electrons (d) Cu⁺: 28 electrons, Cu²⁺: 27 electrons

Write electron configuration

Using the periodic table and the Aufbau principle, write the electron configuration for each element or ion. (a) S: 1s²2s²2p⁶3s²3p⁴, S²⁻: 1s²2s²2p⁶3s²3p⁶ (b) Al: 1s²2s²2p⁶3s²3p¹, Al³⁺: 1s²2s²2p⁶ (c) V: 1s²2s²2p⁶3s²3p⁶4s²3d³, V⁴⁺: 1s²2s²2p⁶3s²3p⁶3d¹ (d) Cu⁺: 1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰, Cu²⁺: 1s²2s²2p⁶3s²3p⁶3d⁹

Key concepts

Periodic Table

The periodic table is an essential tool in chemistry that organizes all known elements by increasing atomic number, which is the number of protons in an element's nucleus. Elements in the same column, or group, have similar chemical properties due to their electron configurations. For instance, when you need to determine the electron configuration for an element like sulfur (S), you start at hydrogen (H), with an atomic number of 1, and follow the rows and columns to sulfur, which has an atomic number of 16.

Each row on the periodic table represents a different energy level that electrons can occupy. As you move from one element to the next, you're essentially adding one more electron into the configuration, following specific rules for how electrons fill the available energy sublevels. An understanding of the periodic table is crucial when explaining how to write ground-state electron configurations.

Aufbau Principle

The Aufbau principle, which in German means 'building up', is a guideline for determining the electron configuration of an atom. It suggests that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. To put this into practice, remember that the order begins with the 1s orbital, followed by the 2s, and so on, filling the 'p', 'd', and 'f' orbitals as they become necessary according to the rules of the periodic table.

The principle accounts for the sequential order seen in the step-by-step solution for atoms and ions like S and Al³⁺. However, remember that there are exceptions to the Aufbau principle, and one should always check the actual electron configurations, particularly for transition metals, such as copper (Cu), which do not always follow the expected pattern due to the energies of the 's' and 'd' subshells.

Atomic Number

The atomic number of an element is fundamental in understanding its properties and is denoted by the letter 'Z'. This number, found above the element symbol on the periodic table, represents the number of protons in the nucleus of an atom and, by extension, the number of electrons in the neutral atom. Learning the atomic number is the first step in writing electron configurations, as seen in the example of vanadium (V), which has an atomic number of 23.

However, for ions, the number of electrons will differ from the atomic number due to the gain or loss of electrons necessary to achieve a full or stable electron shell. This is reflected when determining the electron configuration for ions like S²⁻ or Al³⁺.

Ions and Electron Gain/Loss

Ions are atoms or molecules that have gained or lost electrons, resulting in a net charge. When an atom gains electrons, it becomes a negatively charged ion, or anion, as is the case with S²⁻, which has gained two electrons. Conversely, when an atom loses electrons, it becomes a positively charged ion, or cation, as seen with Al³⁺, which has lost three electrons.

The creation of ions affects their electron configuration. In a cation, electrons are removed from the orbitals in the reverse order of how they were added according to the Aufbau principle, while additional electrons in an anion fill the orbitals following the same principle. The resulting change in the electron configuration is reflected in all following chemical properties and reactions. For example, a copper atom loses an electron to become Cu⁺, leading to a unique configuration that's crucial to understand for tasks like the ones shown in our exercise.