Question

Magnesium atoms lose two electrons when they react. Write the symbol of the ion that is formed. Is it a cation or an anion?

Short answer

The ion formed is \( \text{Mg}^{2+} \), a cation.

Step-by-step solution

Identify the Element

Magnesium is a chemical element with the symbol Mg. It is an alkaline earth metal with an atomic number of 12.

Determine Electron Loss

Magnesium atoms have two electrons in their outer shell. To achieve a stable electron configuration similar to that of a noble gas, magnesium tends to lose these two electrons.

Write the Ion Symbol

When magnesium loses two electrons, it becomes a magnesium ion with a 2+ charge. Thus, the symbol for the ion is \( \text{Mg}^{2+} \).

Identify the Ion Type

Since the magnesium atom loses electrons, it forms a positively charged ion, known as a cation. Cations are positively charged ions formed by the loss of electrons.

Key concepts

Magnesium Ion

When magnesium, which is symbolized by Mg, undergoes a chemical reaction, it transforms into an ion known as magnesium ion. This happens when a magnesium atom loses two electrons from its outer shell.
This transformation is crucial because atoms tend to seek stability. For magnesium, achieving this means having the same electron configuration as a noble gas, which is both stable and low in energy.
The loss of two electrons leads to a change in the charge balance within the atom. Originally neutral, the magnesium atom becomes positively charged because it now has more protons than electrons.
The result is the formation of a magnesium ion denoted by the chemical symbol \( \text{Mg}^{2+} \). The "2+" indicates the loss of two negatively charged electrons, resulting in a net positive charge.

Cation

A cation is a type of ion that carries a positive charge. In chemical reactions, atoms often interact in ways that lead to the formation of ions, and the creation of cations is a common phenomenon.
For any element, when it loses one or more electrons, it forms a cation. Electrons have a negative charge, so losing them results in a positively charged ion.
Magnesium, being an alkaline earth metal, typically forms cations. When a magnesium atom loses its two outermost electrons, it forms a magnesium cation. This process is characterized by more protons (which are positively charged) in the atom than remaining electrons, hence the net positive charge.
Knowing whether an ion is a cation or an anion is important because it affects how the element interacts with other atoms and molecules. Cations like \( \text{Mg}^{2+} \) are often attracted to anions, which are negatively charged ions, leading to the formation of ionic compounds.

Electron Configuration

Understanding electron configuration is key to knowing how and why atoms react to form ions. Electrons are arranged around the nucleus of an atom in specific levels or shells.
For magnesium, with an atomic number of 12, there are 12 electrons surrounding the nucleus in a neutral atom. These electrons are arranged in energy levels, often referred to as shells. The configuration is typically written as \( 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \).
In the case of magnesium, the two electrons in the outermost shell (3s) are the ones that are lost during ion formation. This loss results in an electron configuration akin to neon, \( 1s^2 \, 2s^2 \, 2p^6 \), which is a stable noble gas configuration.
This stable electron configuration is the goal of many chemical reactions, as atoms are more stable and less reactive when they mirror the electron arrangement of noble gases. The electron configuration therefore explains the driving force behind magnesium's formation of a \( \text{Mg}^{2+} \) cation.