Magnesium Atom vs. Magnesium Ion

What's the Difference?

A magnesium atom is a neutral particle that consists of 12 protons, 12 neutrons, and 12 electrons. It is stable and does not carry any charge. On the other hand, a magnesium ion is formed when a magnesium atom loses two electrons. This results in a positively charged ion with a +2 charge. The magnesium ion is smaller in size compared to the magnesium atom due to the loss of two electrons, which reduces the electron cloud surrounding the nucleus. Additionally, the magnesium ion is more reactive than the magnesium atom due to the presence of a positive charge, making it more likely to participate in chemical reactions.


AttributeMagnesium AtomMagnesium Ion
ChargeNeutral (0)Positive (+2)
Number of Electrons1210
Number of Protons1212
Number of Neutrons1212
Atomic Mass24.305 amu24.305 amu
Atomic SymbolMgMg
Electronic Configuration1s² 2s² 2p⁶ 3s²1s² 2s² 2p⁶
Valence Electrons20
Chemical BehaviorReactiveLess Reactive

Further Detail


Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray solid that is highly reactive and belongs to the alkaline earth metals group. Magnesium is an essential element for life, playing a crucial role in various biological processes. In this article, we will compare the attributes of the magnesium atom and the magnesium ion, highlighting their differences and similarities.

Magnesium Atom

The magnesium atom is the neutral form of magnesium, meaning it has an equal number of protons and electrons. It has an atomic mass of approximately 24.31 atomic mass units (amu) and a relatively small atomic radius of about 160 picometers (pm). The atomic radius represents the distance from the nucleus to the outermost electron shell.

Magnesium atoms have a total of 12 electrons, arranged in three energy levels or shells. The first shell contains 2 electrons, while the second and third shells hold 8 and 2 electrons, respectively. The outermost shell, also known as the valence shell, contains the two valence electrons of magnesium. These valence electrons are responsible for the chemical properties and reactivity of the atom.

The magnesium atom has a strong tendency to lose its two valence electrons to achieve a stable electron configuration. By losing these electrons, the magnesium atom forms a positive charge and transforms into a magnesium ion.

Magnesium Ion

The magnesium ion, also known as a cation, is formed when the magnesium atom loses its two valence electrons. As a result, the magnesium ion has a positive charge of +2. This charge is due to the fact that the number of protons in the nucleus remains the same, while the number of electrons decreases by two.

The loss of electrons from the magnesium atom leads to a reduction in the atomic radius of the magnesium ion compared to the atom. The removal of the two valence electrons results in a more compact electron cloud around the nucleus, causing the ionic radius to decrease. The ionic radius of the magnesium ion is approximately 72 pm.

Magnesium ions are highly reactive due to their positive charge. They readily interact with other atoms or ions to form compounds. The most common compound formed by magnesium ions is magnesium oxide (MgO), which is a white solid with various industrial applications.

Physical Properties

When comparing the physical properties of the magnesium atom and the magnesium ion, several differences can be observed. The magnesium atom is a solid metal with a melting point of 650 degrees Celsius (1220 degrees Fahrenheit) and a boiling point of 1090 degrees Celsius (1994 degrees Fahrenheit). It has a density of 1.74 grams per cubic centimeter (g/cm³) and is relatively lightweight.

In contrast, the magnesium ion does not exist as an independent entity in its pure form. It is always found in compounds due to its high reactivity. Therefore, it does not have specific physical properties like melting or boiling points. However, compounds containing magnesium ions may exhibit different physical properties depending on the specific compound.

Chemical Properties

The chemical properties of the magnesium atom and the magnesium ion are significantly different. The magnesium atom, with its two valence electrons, has a strong tendency to lose these electrons and achieve a stable electron configuration. This property makes magnesium a highly reactive metal.

Magnesium atoms readily react with oxygen to form magnesium oxide, a process known as oxidation. This reaction is exothermic, releasing a significant amount of heat. The reaction can be represented by the equation: 2Mg + O₂ → 2MgO.

On the other hand, magnesium ions, with their positive charge, have a strong attraction to negatively charged ions or molecules. They can form ionic compounds with various anions, such as chloride (Cl⁻), sulfate (SO₄²⁻), and carbonate (CO₃²⁻). These compounds are often soluble in water and exhibit different chemical properties depending on the specific anion involved.

Biological Significance

Magnesium is an essential element for life, playing a crucial role in various biological processes. Both the magnesium atom and the magnesium ion are involved in these processes, albeit in different ways.

The magnesium atom is a component of chlorophyll, the pigment responsible for photosynthesis in plants. It is also a cofactor for many enzymes involved in energy metabolism, DNA replication, and protein synthesis. Magnesium ions are required for the proper functioning of nerve cells, muscle contraction, and the maintenance of a healthy heartbeat.

In the human body, magnesium ions are often found complexed with other molecules, such as ATP (adenosine triphosphate), the energy currency of cells. These complexes ensure the stability and availability of magnesium ions for cellular processes.


In conclusion, the attributes of the magnesium atom and the magnesium ion differ significantly. The magnesium atom is a neutral species with two valence electrons, while the magnesium ion is a positively charged cation formed by the loss of these electrons. The physical and chemical properties of the two entities also vary, with the magnesium atom being a solid metal and the magnesium ion being highly reactive and often found in compounds. Understanding the differences between the magnesium atom and the magnesium ion is essential for comprehending their roles in various scientific and biological contexts.

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