Magnéziumion

Magnéziumion, or magnesium ion, is the Mg2+ cation formed when magnesium atoms lose two electrons. In aqueous solutions, Mg2+ is highly hydrated and typically exists as the octahedral hexaaqua complex [Mg(H2O)6]2+. The ion appears in many inorganic salts, such as magnesium chloride (MgCl2), magnesium sulfate (MgSO4), and magnesium carbonate (MgCO3).

Geochemically and geologically, magnesium ions arise from the weathering of minerals such as magnesite and dolomite and are common constituents of seawater, where Mg2+ is present at about 0.05 mol/L. In solid compounds, Mg2+ often adopts octahedral coordination in crystal lattices.

Biologically, Mg2+ is an essential cofactor for hundreds of enzymes and participates in stabilizing structures of nucleotides (ATP, DNA, RNA) and ribosomes. It is required for photosynthesis in plants as the central ion of chlorophyll. Mg2+ also influences nerve and muscle function and helps regulate ion channels and signal transduction.

Nutrition and health: Magnesium intake is essential for health. Dietary sources include leafy greens, nuts, seeds and whole grains. Recommended daily intake varies by age and sex, roughly 300–420 mg elemental magnesium for adults. Deficiency can cause neuromuscular symptoms and arrhythmias; excess, mainly in people with kidney impairment or excessive supplement use, can lead to hypermagnesemia with hypotension or respiratory depression.

Notes: In water treatment, Mg2+ contributes to hardness and scaling, and removal may be desired in some processes. In medicine, Mg2+ is used therapeutically, for example as magnesium sulfate for electrolyte disorders or as a laxative. The ion plays a fundamental role in biology and earth sciences.