MAGNESIUM

Name: Magnesium (refers to the Greek region of Magnesia)

Symbol: Mg

Group: 2

Period: 3

Block: s

Category: Alkaline earth metals

Atomic number: 12

Atomic mass: 23.405 u

Electrons per shell: 2, 8, 2

Electronegativity: 1.31

Density: 1.738 g/cc

Melting point: 650ºC

Boiling point: 1091ºC

Thermal conductivity: 156 W (m·K)

Electrical conductivity: 2.3 × 10^7 S/m

Magnetic order: Paramagnetic

Ordinary state: Solid

Oxidation states: +2, +1

Mohs hardness: 2 (depending on the source, 1.5–2.5)

Vickers Hardness: No data

Brinell Hardness: 260 MPa (pure)

Most stable isotopes: Mg-24 (79%), Mg-25 (10%), Mg-26 (11%)

Discoverer: Humphry Davy, English (1808)

Magnesium, with atomic number 12, stands out as the alkaline earth element closest to a typical metal, reminiscent of aluminum and, to a lesser extent, zinc in its properties, unlike beryllium, which is reminiscent of metalloids such as silicon, germanium, and boron. As the lightest structural metal used on a large scale in industry, surpassed only by iron (in the form of steel) and aluminum in terms of uses, magnesium cannot match the latter's versatility. It is rarely used in its pure form, but shines as a secondary component in alloys, where it significantly improves their properties. Its main advantage is its low density, approximately two-thirds that of aluminum, making it a key material in weight-critical applications.

In the cosmic realm, magnesium, like other elements with even atomic numbers less than 28, is abundantly formed in massive stars during the burning of silicon, following the CNO cycle. It acts as an intermediary between neon and silicon, with stable nuclei unaffected by these elements, which explains its abundance both on Earth and in the observable universe. Furthermore, it is a direct precursor to aluminum, generated by the capture or fusion of a proton (H¹). As a siderophile element, magnesium is widely found in the Earth's crust, embedded in complex silicates alongside silicon, alkali metals, and other alkaline earth metals. The discovery of magnesium is attributed to the prominent English chemist Humphry Davy, who in the 19th century also isolated calcium, strontium, and barium. His work marked a milestone in chemistry, consolidating magnesium as an element of increasing importance in metallurgy and other scientific disciplines.

Magnesium, in its pure form, exhibits a whitish metallic luster that reflects its nature as an alkaline earth metal. As an electrical and thermal conductor, it meets expectations based on its electron configuration, although its performance is significantly inferior to that of aluminum. Its shiny appearance makes it attractive, but its true distinction lies in its lightness. Among metals stored in large quantities, such as ingots, bars, or rolled sheets, magnesium is the lightest, both due to its low nuclear density and its true density, approximately two-thirds that of aluminum. This characteristic makes it a valuable material in applications where weight is a critical factor.

In terms of stability, magnesium remains intact in dry air for years, and in water, it reacts very slowly thanks to a passivating oxide layer. However, this layer is weaker than that of aluminum and much less robust than that of chromium or titanium, which limits its chemical resistance. Although it does not require additional coatings such as paints, oils, or inert atmospheres to remain in its elemental state, pure magnesium lacks significant practical applications due to its softness. With low resistance to scratching, pressure, stretching, and deformation, it is mechanically brittle, although it compensates with its remarkable ductility and malleability that allow it to be easily formed into large sheets or plates.

Magnesium's disadvantages include its high reactivity, typical of alkaline earth metals, which makes it susceptible to corrosion in aggressive media. Furthermore, it is flammable, especially in powder or shavings, and its resistance to high temperatures is limited, restricting its use in extreme environments. These characteristics make magnesium more valuable as an alloying agent, improving the properties of other metals, than as a pure material.

Knowledge and exploitation of magnesium compounds dates back to ancient times, although their use in more refined and scientific forms is relatively recent. One of its most famous examples in the medical field is milk of magnesia, a compound that, thanks to the neutralizing action of Mg(OH)₂, counteracts excess hydrochloric acid (HCl) in the stomach, helping to relieve gastric disorders. Among its basic compounds, magnesium monoxide (MgO) stands out for its use as a refractory material in the manufacture of crucibles, offering a much higher thermal resistance than pure metallic magnesium, making it ideal for processes that require withstanding extreme temperatures. This metal has a remarkable ability to generate light when subjected to impact or abrasion, a phenomenon that, historically, found application in the early stages of photography with the preparation of so-called "flash powder," a mixture that, upon rapid reaction with oxygen (O₂), produced vigorous oxidation capable of emitting intense light in fractions of a second. This property not only marked a milestone in photographic lighting but was also used in scientific demonstrations and shows.

In a more practical and enduring context, magnesium is used as a spark source in survival tools, both military and civilian, where, when struck against a steel flint, it releases incandescent particles capable of igniting dry tinder even under adverse conditions. This method, safe except for the inherent risk of fire, remains in use thanks to its reliability and simplicity. In the construction field, non-organic magnesium finds its main application as an essential component in cements and concretes, either in the form of natural compounds or in simple manufacturing, contributing to the strength and durability of large-scale structures.

Within metallurgy, magnesium has given rise to high-tech alloys, among which "Elektron" stands out, originally developed in Germany in 1908 by Gustav Pistor and Wilhelm Moschel, although often mistakenly attributed to British engineering. It is a magnesium-based alloy in which aluminum acts as the main alloying element, accompanied in varying degrees by zinc (Zn), yttrium (Y), silver (Ag), manganese (Mn), and lanthanides such as gadolinium (Gd), depending on the desired performance. Zinc, in particular, is almost always present, given its excellent compatibility with both base metals.

As with aluminum, magnesium's corrosion resistance decreases as other metals are incorporated, even if they are stronger in their pure state. In return, these additions increase mechanical strength, hardness, and high-temperature performance. Within this family, there are aluminum-magnesium alloys without a fixed designation in which the Mg content is increased to the structural limit before losing strength, with the addition of elements such as copper (Cu) or zinc to optimize rigidity and thermal tolerance.

These alloys played a fundamental role in the high-performance engine industry before World War II, gradually replacing steel engines in aircraft due to their lower density, which allowed for the manufacture of larger engine blocks without compromising overall weight. Their use subsequently spread to land vehicles and, to a lesser extent, maritime vehicles, always due to the advantage of lightness over the mechanical strength of steel. Although they are not superior to steel in absolute strength, their lower density allows for larger displacement designs and, therefore, greater specific power.

Today, aluminum-magnesium alloys are used not only for engine blocks but also for the manufacture of complete bodies and chassis in high-end vehicles, competing with materials such as carbon fiber. However, unlike carbon fiber, metal alloys can be hot-formed, offering greater possibilities for the production of complex components. Its use extends to aeronautics, the luxury automotive industry, and the manufacturing of helicopters, radars, and spacecraft, consolidating magnesium as a key element in modern engineering.