![]() However, this reaction is much less dramatic than the reactions of the alkali metals with water, because the magnesium hydroxide builds up on the surface of the magnesium metal and inhibits further reaction. When finely powdered, magnesium reacts with water to produce hydrogen gas: The malleability of polycrystalline magnesium can also be significantly improved by reducing its grain size to ca. It becomes much more malleable when alloyed with small amounts of other metals, such as 1% aluminium. Pure polycrystalline magnesium is brittle and easily fractures along shear bands. Magnesium has the lowest melting (923 K (650 ☌)) and the lowest boiling point (1,363 K (1,090 ☌)) of all the alkaline earth metals. Įlemental magnesium is a gray-white lightweight metal, two-thirds the density of aluminium. Magnesium compounds are used medicinally as common laxatives and antacids (such as milk of magnesia), and to stabilize abnormal nerve excitation or blood vessel spasm in such conditions as eclampsia. Hundreds of enzymes require magnesium ions to function. Magnesium ions interact with polyphosphate compounds such as ATP, DNA, and RNA. This element is the eleventh most abundant element by mass in the human body and is essential to all cells and some 300 enzymes. It is the third most abundant element dissolved in seawater, after sodium and chlorine. Magnesium is the eighth most abundant element in the Earth's crust and the fourth most common element in the Earth (after iron, oxygen and silicon), making up 13% of the planet's mass and a large fraction of the planet's mantle. When such stars explode as supernovas, much of the magnesium is expelled into the interstellar medium where it may recycle into new star systems. ![]() In the cosmos, magnesium is produced in large, aging stars by the sequential addition of three helium nuclei to a carbon nucleus. ![]() It is less dense than aluminium and is used primarily as a component in strong and lightweight alloys that contain aluminium. The metal is obtained mainly by electrolysis of magnesium salts obtained from brine. The free metal burns with a brilliant-white light. It reacts readily with air to form a thin passivation coating of magnesium oxide that inhibits further corrosion of the metal. Like the other alkaline earth metals (group 2 of the periodic table) it occurs naturally only in combination with other elements and it almost always has an oxidation state of +2. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Using the chemical formula of the compound and the periodic table of elements, we can add up the atomic weights and calculate molecular weight of the substance.Magnesium is a chemical element with the symbol Mg and atomic number 12. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass. This is not the same as molecular mass, which is the mass of a single molecule of well-defined isotopes. This is how to calculate molar mass (average molecular weight), which is based on isotropically weighted averages. The atomic weights used on this site come from NIST, the National Institute of Standards and Technology. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula. ![]() When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. This site explains how to find molar mass.įinding molar mass starts with units of grams per mole (g/mol). The reason is that the molar mass of the substance affects the conversion. To complete this calculation, you have to know what substance you are trying to convert. The percentage by weight of any atom or group of atoms in a compound can be computed by dividing the total weight of the atom (or group of atoms) in the formula by the formula weight and multiplying by 100.Ī common request on this site is to convert grams to moles. If the formula used in calculating molar mass is the molecular formula, the formula weight computed is the molecular weight. These relative weights computed from the chemical equation are sometimes called equation weights. In chemistry, the formula weight is a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a chemical formula by the number of atoms of that element present in the formula, then adding all of these products together.įormula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction.
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