Strontium Oxide

Strontium oxide , which has the chemical formula SrO (not to be confused with strontium peroxide, which is SrO2), is the product of the oxidative reaction between this metal and the oxygen present in the air at room temperature: 2Sr(s) + O2(g) ) → 2 SRO.

A piece of strontium burns upon contact with air as a result of its high reactivity, and since it has an electronic configuration of the ns2 type, it readily produces its two valence electrons, especially the oxygen diatomic molecule.

Strontium Oxide
Strontium Oxide

If the surface area of ​​the metal is increased by spraying it into a finely divided powder, the reaction occurs immediately, and even burns with an intense red flame. Strontium, the metal that takes part in this reaction, is a metal of group 2 of the periodic table.

This group is formed by the elements known as alkaline earths. The first of the elements to lead the group is beryllium, followed by magnesium, calcium, strontium, barium, and finally radium. These elements are of a metallic nature and, as a rule, to remember them, you can use the expression:”Mr. Becambra “.

The expression “Sr”, pronounced by none other than strontium metal (Sr), is a highly reactive chemical element not found naturally in its pure form, but with other elements in the environment or with its environment. combined which gives rise to its salts, nitrides and oxides. For this reason, minerals and strontium oxide are compounds in which strontium is found in nature.

physical and chemical properties

Strontium oxide is a white, porous and odorless solid compound and, depending on its physical treatment, can be found on the market in the form of a fine powder, in the form of crystals or in the form of nanoparticles.

Its molecular weight is 103.619 g/mol and it has a high refractive index. It has high melting (2531 °C) and boiling (3200 °C) points, which translates into a strong bonding relationship between strontium and oxygen. This high melting point makes it a thermally stable material.

basic oxide

It is a highly basic oxide; This means that it reacts with water at room temperature to form strontium hydroxide (Sr(OH) 2):

SrO(s) + H 2 O (L) → Sr(OH) 2


It reacts or retains moisture, an essential characteristic of hygroscopic compounds. Therefore, strontium oxide has a high reactivity with water.

In other solvents – for example, alcohols such as ethanol from pharmacy or methanol – is slightly soluble; Whereas in solvents such as acetone, ether or dichloromethane, it is insoluble.

Why is this? Because metal oxides – and even more so those formed from alkaline earth metals – are polar compounds and therefore interact to a greater degree with polar solvents.

Not only can it react with water, but with carbon dioxide, to produce strontium carbonate:

SrO (s) + CO2 (g) → SrCO3 (s)

Reacts with acids – such as dilute phosphoric acid – to produce salts of strontium phosphate and water:

3SO (s) + 2 H3PO4 (diluted) → Sr3 (PO4) 2 (s) + 3H2O (g)

These reactions are exothermic, which is why the high temperature causes water to evaporate.

chemical composition

The chemical structure of a compound describes how its atoms are arranged in space. In the case of strontium oxide, it has a crystal structure similar to that of rock salt, table salt or sodium chloride (NaCl).

In contrast to NaCl, monovalent salts—which are anions and anions of the same magnitude (+1 for Na and -1 for Cl)—condensate SrO, to 2+ for Sr and -2 for O ( O2-, anion oxide).

Each O2- ion (colored red) in this structure is surrounded by another six volcanic oxide ions, their resulting octahedral ions Sr2+ (green), smaller. This package or arrangement is known as the face-centered unit cubic cell (ccc).

link type

The chemical formula of strontium oxide is SrO, but this does not fully explain the chemical structure or the type of bond existing.

In the previous section it was mentioned that it has a gem-like structure; That is, a crystal structure very common to many salts.

Therefore, the bond type is mainly ionic, which would explain why this oxide has high melting and boiling points.

Since the bond is ionic, it is the electrostatic interaction that holds the strontium and oxygen atoms together: Sr2 + O2-.

If this bond was covalent, the compound could be represented with bonds in its Lewis structure (except for the non-shared electron pair).


It is necessary to estimate the physical properties of a compound to determine its potential applications in industry; Therefore, these are a gross reflection of their chemical properties.

substitute for lead

Strontium oxide, thanks to its high thermal stability, finds many applications in the ceramic, glass and optical industries.

In these industries it is mainly used as a replacement for lead and as an additive that gives better color and viscosity to raw materials of products.

What products? The list would be no end, as in any of these containing glass, enamel, ceramic or crystals in any of its pieces, strontium oxide could be useful.

Aerospace industry

As it is a very porous solid, it can disperse small particles, and thus offers a range of possibilities in the manufacture of materials, therefore should be considered by the aerospace industry.


The same pore allows it to be used as a catalyst (accelerator of chemical reactions) and as a heat exchanger.

electronic purpose

Strontium oxide also serves as a source of pure strontium production for electronic purposes, thanks to the ability of this metal to absorb X-rays; and for the industrial preparation of its hydroxide, Sr(OH)2, and its peroxide, SrO2.

health risk

It is a corrosive compound, so it can burn with simple physical contact on any part of the body. It is very sensitive to moisture and should be stored in dry and cool places.

The salt products of the reaction of this oxide with various acids behave in organisms as well as calcium salts, and are stored or removed by similar mechanisms. At the moment, strontium oxide by itself does not represent major health risks.