Difference Between Magnesia and Magnesium

The key difference between magnesia and magnesium is that magnesia is the inorganic compound magnesium hydroxide, whereas magnesium is a chemical element.

Magnesia is a chemical compound that is derived from magnesium. Both are inorganic components in inorganic chemistry.

1. Overview and Key Difference
2. What is Magnesia
3. What is Magnesium
4. Side by Side Comparison – Magnesia vs Magnesium in Tabular Form
5. Summary

What is Magnesia?

Magnesia or milk of magnesia is magnesium hydroxide. It is a chemical compound having the chemical formula Mg(OH)2. This substance is a white solid, but unlike magnesium oxide, this compound is not hygroscopic because it has low water solubility. Magnesia occurs in nature as the mineral brucite.

We can produce this compound easily by adding water to magnesium oxide. Or else, we can produce it by combining a solution of magnesium salts with alkaline water. Thus, this reaction gives a precipitate of magnesium hydroxide. However, in a commercial scale, we produce this material by treating seawater with lime. Moreover, this reaction gives tons of magnesium hydroxide.

When considering the uses of this compound, it is mainly important as the precursor for the production of magnesium oxide. In its suspension form, this material is important as either an antacid or as a laxative. Moreover, it is useful as a food additive. In addition, this material is important to neutralize acidic wastewater.

What is Magnesium?

Magnesium is the chemical element having atomic number 12 and chemical symbol Mg. This chemical element occurs as a grey-shiny solid at room temperature. It is in group 2, period 3 in the periodic table. Therefore, we can name it as an s-block element. Further, magnesium is an alkaline earth metal (group 2 chemical elements are named alkaline earth metals). The electron configuration of this metal is [Ne]3s².

Difference Between Magnesia and Magnesium

Figure 01: Ductile and Brittle Forms of Magnesium Metal

Magnesium metal is an abundant chemical element in the universe. Naturally, this metal occurs in combination with other chemical elements. Besides, the oxidation state of magnesium is +2. The free metal is highly reactive, but we can produce it as a synthetic material. It can burn, producing very bright light. We call it a brilliant white light. We can obtain magnesium by electrolysis of magnesium salts. These magnesium salts can be obtained from brine.

Magnesium is a lightweight metal, and it has the lowest values for melting and boiling points among alkaline earth metals. This metal is also brittle and easily undergoes fracture along with shear bands. When it is alloyed with aluminium, the alloy becomes very ductile.

Figure 02: Magnesium Sheets

The reaction between magnesium and water is not as rapid as calcium and other alkaline earth metals. When we submerge a piece of magnesium in water, we can observe hydrogen bubbles emerge from the metal surface. However, the reaction speeds up with hot water. Moreover, this metal can react with acids exothermally, e.g., hydrochloric acid (HCl).

What is the Difference Between Magnesia and Magnesium?

Although the terms magnesia and magnesium sound closely similar they are two different terms with different chemical properties. Magnesia or milk of magnesia is magnesium hydroxide while magnesium is the chemical element having atomic number 12 and chemical symbol Mg. The key difference between magnesia and magnesium is that magnesia is the inorganic compound magnesium hydroxide whereas magnesium is a chemical element.

Furthermore, magnesia can occur naturally as the mineral brucite while magnesium occurs in minerals such as brucite, dolomite, carnalite, etc. and mainly in seawater and brine.

The below infographic lists the differences between magnesia and magnesium in tabular form.

Summary – Magnesia vs Magnesium

Magnesia is a compound made from magnesium. The key difference between magnesia and magnesium is that magnesia is the inorganic compound magnesium hydroxide whereas magnesium is a chemical element.