Question

Write the electron configuration for each ion. a. \(\mathrm{Cl}^{-}\) b. \(\mathrm{P}^{3-}\) c. \(\mathrm{K}^{+}\) d. \(\mathrm{Mo}^{3+}\) e. \(V^{3+}\)

Short answer

a. \text{Cl}^-: 1s^2 2s^2 2p^6 3s^2 3p^6, b. \text{P}^{3-}: 1s^2 2s^2 2p^6 3s^2 3p^6, c. \text{K}^+: 1s^2 2s^2 2p^6 3s^2 3p^6, d. \text{Mo}^{3+}: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^1 4d^2, e. V^{3+}: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^2.

Step-by-step solution

Recognizing the Neutral Atom

Before writing the electron configuration for an ion, identify the electron configuration for the neutral atom. Chlorine has 17 electrons, Phosphorus has 15, Potassium has 19, Molybdenum has 42, and Vanadium has 23.

Determining the Electron Configuration for Cl-

The chloride ion has one more electron than the neutral chlorine atom. Write the configuration for 18 electrons as if it were Argon: 1s^2 2s^2 2p^6 3s^2 3p^6.

Determining the Electron Configuration for P3-

The phosphide ion has three more electrons than the neutral phosphorus atom, giving it 18 electrons total. Write the electron configuration as if it were Argon: 1s^2 2s^2 2p^6 3s^2 3p^6.

Determining the Electron Configuration for K+

The potassium ion has one less electron than the neutral potassium atom. Write the configuration for 18 electrons as if it were Argon: 1s^2 2s^2 2p^6 3s^2 3p^6.

Determining the Electron Configuration for Mo3+

The molybdenum ion has three fewer electrons than the neutral molybdenum atom, meaning it has 42 - 3 = 39 electrons. Consult the periodic table and write the electron configuration for 39 electrons, removing electrons from the highest energy levels first: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^1 4d^5, but since it lost 3 electrons, the correct configuration ends with 5s^1 4d^2.

Determining the Electron Configuration for V3+

The vanadium ion has three fewer electrons than the neutral vanadium atom, meaning it has 23 - 3 = 20 electrons. Write the electron configuration for these 20 electrons: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^2.

Key concepts

Chemical Ions

Chemical ions are atoms or molecules that have gained or lost one or more electrons, resulting in a net electrical charge. In their pursuit to reach a more stable, lower energy state, atoms will often either donate or accept electrons. As a result, cations, with a positive charge, are formed by losing electrons, and anions, with a negative charge, are created by gaining electrons.

Understanding how ions form is crucial in chemistry, as ions are fundamental in the composition of salts and are widely involved in chemical reactions, particularly in the transfer of energy in cells and batteries. The process of gaining or losing electrons to form ions directly relates to the element's position on the periodic table and ultimately determines the chemical and physical properties of the substance.

Electron Configuration Steps

Electron configuration represents the distribution of electrons among the orbital shells and subshells of atoms. Here are the essential steps you should follow when writing electron configurations for ions:

1. Identify the total number of electrons in the neutral atom from its atomic number on the periodic table.
2. Determine the change in the number of electrons to form the ion (gain or loss).
3. Add electrons to the neutral atom's configuration (for anions) or remove electrons from the valence shell of the neutral atom (for cations).
4. Write down the new electron configuration, ensuring that the added or removed electrons respect the aufbau principle, the Pauli exclusion principle, and Hund's rule.

An essential part of this process is recognizing that electrons are added or removed according to their energy levels, with the valence shell electrons being the first to go in cations, or the outermost shell being filled first in anions.

Periodic Table

The periodic table is a fundamental tool in chemistry that organizes all known elements by increasing atomic number and groups them based on similar electron configurations and chemical properties. Columns, or groups, indicate elements with the same number of electrons in their outermost shell, which dictates how they will bond and react with other elements. On the other hand, rows, or periods, represent elements with the same number of orbital shells.

When it comes to determining the electron configuration for ions, the periodic table offers valuable insight. It assists in predicting how many electrons need to be added or removed to achieve a full valence shell, which is often equivalent to the nearest noble gas electron configuration. For transition metals, the table provides a visual aid in understanding why specific electrons are removed first when forming cations, as seen in elements like Molybdenum and Vanadium.