Strontium Oxide (SrO): Properties, Applications and Risks

He strontium oxide , whose chemical formula is 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) → 2SrO (s).

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

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 burning with an intense reddish flame. Strontium, the metal that participates in this reaction, is a metal of group 2 of the periodic table.

This group is constituted by the elements known as alkaline earth. The first of the elements that leads the group is beryllium, followed by magnesium, calcium, strontium, barium, and finally, radium. These elements are of a metallic nature and, as a mnemonic rule to remember them, you can use the expression:"Mr. Becambara."

The"Sr"alluded to by the expression is none other than strontium metal (Sr), a highly reactive chemical element that is naturally not found in its pure form, but combined with other elements of the environment or its environment to give rise to its salts, nitrides and oxides.

For this reason, minerals and strontium oxide are the compounds in which strontium is found in nature.

Index

  • 1 Physical and chemical properties
    • 1.1 Basic oxide
    • 1.2 Solubility
  • 2 Chemical structure
  • 3 Type of link
  • 4 Applications
    • 4.1 Lead substitute
    • 4.2 Aerospace industry
    • 4.3 Catalyst
    • 4.4 Electronic purposes
  • 5 Health risks
  • 6 References

Physical and chemical properties

Strontium oxide is a white, porous and odorless solid and, depending on its physical treatment, can be found on the market as fine powder, as crystals or as 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 strong bonding interactions 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 at room temperature with the water to form strontium hydroxide (Sr (OH) 2):

SrO (s) + H2O (l) → Sr (OH) 2

Solubility

It also 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 the pharmacy or methanol-are slightly soluble; while in solvents such as acetone, ether or dichloromethane, it is insoluble.

Why is this so? Because the metal oxides â €"and even more those formed from the alkaline earth metals â €"are polar compounds and therefore interact in a better degree with the polar solvents.

Not only can it react with water, but also with carbon dioxide, producing strontium carbonate:

SrO (s) + CO2 (g) → SrCO3 (s)

Reacts with acids - such as diluted phosphoric acid - to produce the salt of strontium phosphate and water:

3SrO (s) + 2 H3PO4 (dil) → Sr3 (PO4) 2 (s) + 3H2O (g)

These reactions are exothermic, which is why the water produced evaporates at high temperatures.

Chemical structure

The chemical structure of a compound explains how is the arrangement of its atoms in space. In the case of strontium oxide, it has a crystalline structure like rock salt, the same as table salt or sodium chloride (NaCl).

Unlike NaCl, monovalent salt - that is, with cations and anions of a magnitude of charge (+1 for Na and -1 for Cl) -, SrO is divalent, with charges of 2+ for Sr, and of -2 for O (O2-, anion oxide).

In this structure each O2- ion (of red color) is surrounded by six other voluminous oxides ions, lodging in their resulting octahedral interstices the ions Sr2 + (green), smaller. This package or arrangement is known as the unit cubic cell centered on the faces (ccc).

Type of link

The chemical formula of strontium oxide is SrO, but it does not explain absolutely the chemical structure or the type of bond that exists.

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

Therefore, the type of bond is predominantly ionic, which would clarify why this oxide has high melting and boiling points.

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

If this link were covalent, the compound could be represented with bonds in its Lewis structure (omitting the non-shared electron pairs of oxygen).

Applications

The physical properties of a compound are essential to predict what its potential applications in the industry would be; therefore, these are a macro reflection of their chemical properties.

Lead substitute

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

Its use in these industries is mainly intended to replace lead and be an additive that gives better colors and viscosities to the raw material of the products.

What products? The list would have no end, because in any of these that have glasses, enamels, ceramics or crystals in any of its pieces, the strontium oxide can be useful.

Aerospace industry

As it is a very porous solid it can intersperse smaller particles, and thus provide a range of possibilities in the formulation of materials, so light as to be considered by the aerospace industry.

Catalyst

That same porosity allows it to have potential uses as a catalyst (accelerator of chemical reactions) and as a heat exchanger.

Electronic purposes

The 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 risks

It is a corrosive compound, so it can cause burns with simple physical contact on any part of the body. It is very sensitive to humidity and should be stored in dry and cold spaces.

The salts product of the reaction of this oxide with different acids behave in the organism as well as the calcium salts, and are stored or expelled by similar mechanisms.

At the moment, strontium oxide by itself does not represent major health risks.

References

  1. American Elements. (1998-2018). American Elements. Retrieved on March 14, 2018, from American Elements: americanelements.com
  2. AllReactions Retrieved on March 14, 2018, from AllReactions: allreactions.com
  3. Shiver & Atkins. (2008). Inorganic Chemistry In The structures of simple solids (Fourth ed., Page 84). Mc Graw Hill.
  4. ATSDR. Retrieved on March 14, 2018, from ATSDR: atsdr.cdc.gov
  5. Clark, J. (2009). chemguide. Retrieved on March 14, 2018, from chemguide: chemguide.co.uk
  6. Tiwary, R., Narayan, S., & Pandey, O. (2007). Preparation of strontium oxide from celestite: A review. Materials Science, 201-211.
  7. Chegg Inc. (2003-2018). Chegg Study. Retrieved on March 16, 2018, from Chegg Study: chegg.com


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