Sodium oxide is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula Na₂ O. It is used in

ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...

s and

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...

es. It is a white solid but the compound is rarely encountered. Instead "sodium oxide" is used to describe components of various materials such as glasses and fertilizers which contain oxides that include sodium and other elements.

Structure

The structure of sodium oxide has been determined by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

. Most

alkali metal oxide The alkali metals react with oxygen to form several different compounds: suboxides, oxides, peroxides, sesquioxides, superoxides, and ozonides. They all react violently with water. Alkali metal suboxides * Hexarubidium monoxide (Rb6O) h * No ...

s M₂O (M = Li, Na, K, Rb) crystallise in the

antifluorite structure In solid state chemistry, the fluorite structure refers to a common motif for compounds with the formula MX2. The X ions occupy the eight tetrahedral interstitial sites whereas M ions occupy the regular sites of a face-centered cubic (FCC) structure ...

. In this motif the positions of the

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

s and cations are reversed relative to their positions in CaF₂, with

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

ions tetrahedrally coordinated to 4 oxide ions and oxide cubically coordinated to 8 sodium ions.

Preparation

Sodium oxide is produced by the reaction of

with sodium hydroxide, sodium peroxide, or

sodium nitrite Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite ...

: : 2 NaOH + 2 Na → 2 Na₂O + H₂ To the extent that NaOH is contaminated with water, correspondingly greater amounts of sodium are employed. Excess sodium is distilled from the crude product. A second method involves heating a mixture of sodium azide and sodium nitrate: : 5NaN₃ + NaNO₃ → 3Na₂O + 8N₂ Burning sodium in

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...

produces a mixture of Na₂O and sodium peroxide (Na₂O₂).

Applications

Glassmaking

Glasses are often described in terms of their sodium oxide content although they do not really contain Na₂O. Furthermore, such glasses are not made from sodium oxide, but the equivalent of Na₂O is added in the form of "soda" ( sodium carbonate), which loses carbon dioxide at high temperatures: : Na₂CO₃ → Na₂O + CO₂ : Na₂O + SiO₂ → Na₂SiO₃ : Na₂CO₃ + SiO₂ → Na₂SiO₃ + CO₂ A typical manufactured

contains around 15% sodium oxide, 70% silica (

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

), and 9% lime (

calcium oxide Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term "''lime''" connotes calcium-containing inorganic ...

). The sodium carbonate "soda" serves as a flux to lower the temperature at which the silica mixture melts. Such soda-lime glass has a much lower melting temperature than pure silica and has slightly higher elasticity. These changes arise because the Na₂ iO₂sub>x iO₃based material is somewhat more flexible.

Reactions

Sodium oxide reacts readily and irreversibly with water to give sodium hydroxide: : Na₂O + H₂O → 2 NaOH Because of this reaction, sodium oxide is sometimes referred to as the base anhydride of sodium hydroxide (more archaically, "anhydride of caustic soda").

References

{{DEFAULTSORT:Sodium Oxide Oxides Sodium compounds Fluorite crystal structure