THE strontium, symbol Sr and atomic number 38, it is a alkaline earth metal, gray in color, whose chemical behavior is similar to the other elements of group 2. Despite being one of the most present elements in the earth's crust, few strontium ores are known.
In previous decades, there was great demand for strontium, because was applied in cathode ray tubes of classic color tube televisions. However, the take-up of more modern flat-panel models has substantially reduced the demand for this metal. Today, its greatest use is in pyrotechnics, due to the characteristic red flame produced when burned.
Read too: Francium — properties of this alkali metal of the seventh period of the Periodic Table
strontium summary
It is an alkaline earth metal with a grayish color.
In its metallic form, it is malleable, ductile and quite fragile.
Its chemical behavior sometimes resembles the alkali metal sodium, At.
Despite being the 15th most abundant element, few ores of strontium are known.
Its main ores are celestite and strontianite.
Much of the strontium is used in the manufacture of fireworks.
Strontium had great utility in the manufacture of tube televisions.
It resembles calcium in the human body, depositing in bones.
Strontium properties
Symbol: Mr.
atomic number: 38.
atomic mass: 87.62 c.m.u.
Fusion point: 767°C.
Boiling point: 1384°C.
Eletronic distribution: [Kr] 5s2.
electronegativity: 0,95.
chemical series: alkaline earth metal, group 2, representative element, s-block.
Strontium Characteristics
Strontium is an alkaline earth metal of grayish coloring, malleable, ductile and quite fragile. In contact with air, the shiny surface of strontium metallic quickly tarnishes.
Strontium's chemical behavior resembles the alkali metal sodium, Na, although it is slightly less reactive. For example, strontium reacts with water and acids, forming gas H2, as shown in the following reaction.
Mr (s) + H2O (l) → SrO (s) + H2 (g)
Another point of similarity with sodium lies in its dissolution in ammonia, NH3, liquid, which generates a blue solution.
When heated, like the other elements of group 2, the Strontium is able to react with the gases oxygen and nitrogen, in addition to sulfur (S8) and halogens, as shown below.
2 Mr + O2 → 2 Mr
3 Mr + N2 → Mr3No2
8 Mr + S8 → 8 Mr.
Mr + X2 → MrX2 X = F, Cl, Br, I
However, like calcium and barium, it differs from two lighter alkaline earth metals, beryllium and magnesium, in the reaction with hydrogen gas, H2. While the heavier alkaline earth metals (Ca, Sr and Ba) react, upon heating, with H2 to form a hydride (like, for example, SrH2), magnesium and beryllium require other experimental conditions to do so.
Obtaining Strontium
Although strontium is one of the most abundant elements in Earth's crust, ranking 15th, with about 340 ppm, Few strontium ores are known. The most common are celestite (SrSO4) and strontianite (SrCO3). You main producers of this metal are:
Spain (86 thousand tons in 2020);
China (50 thousand tons in 2020);
Mexico (38 thousand tons in 2020);
Iran (35 thousand tons in 2020).
Read too: Carbon — one of the most abundant elements in the universe
Strontium applications
Currently, about 30% of the strontium produced is intended for use in pyrotechnics. This is because this metal has a very characteristic red flame, described as crimson, scarlet or crimson.
In industrial application, strontium carbonate is sintered (pulverized and heated) with iron oxide. to form ferrite (or ceramic) magnets, used in refrigerator magnets, speakers, and small motors electrical. Strontium titanate, SrTiO3, is used as a diamond simulator, while strontium chloride, SrCl2, is used in toothpastes for sensitive teeth.
It can be said that the The demand for strontium in the market has varied greatly over the years.. This is because SrO, strontium oxide, was used in the cathode ray tubes of old tube televisions. Its purpose was to block X-ray emissions on the front glass without compromising transparency. However, the arrival of flat-panel televisions virtually extinguished the use of strontium in TVs. Currently, only a small sample of strontium carbonate, SrCO3, is used in these devices.
precautions with strontium
At the Human Body, strontium is absorbed similarly to calcium, its neighbor in group 2, being, in most cases, deposited in the bones. This makes strontium quite innocuous, and the possibility of using strontium in the prevention and treatment of bone diseases such as osteoporosis has even been studied.
However, this similarity with calcium makes its radioactive isotope of greater half life (90Sr), produced in nuclear reactors and in the fission of uranium, a dangerous agent that causes bone cancer. However, in controlled amounts, this isotope, together with the isotope 89Sir, it can be used in bone radiation therapy.
Read too: Lead — properties of this heavy metal of wide applicability
history of strontium
THE The name strontium refers to the Scottish village of Strontian (Sròn an t-Sìthein), thus being the only element named after a location in the United Kingdom. In 1790, the Northern Irishman Adair Crawford noticed that ores extracted from the lead mines of Strontian, which were sold as “aerated barites”, they actually had different properties from the barium ores known until then.
This was confirmed by chemists Friedrich Gabriel Sulzer in 1791 and Thomas Charles Hope in 1793, who named the mineral strontianite. strontianite) and stroncita (from English strontite), respectively.
already the strontium was first isolated by Humphry Davy in 1808, using a technique of electrolysis used by Jacob Berzelius and Magnums Martin af Pontin to produce calcium.
Davy used the method to isolate four alkaline earth metals, which he named barium, strontium, calcium and magnesium (now known as magnesium).
Solved exercises on strontium
question 1
(Enem 2019) Radioactive pollution comprises more than 200 nuclides, and from the point of view of environmental impact, cesium-137 and strontium-90 stand out. The greatest contribution of anthropogenic radionuclides to the marine environment occurred during the 1950s and 1960s, as a result of nuclear tests carried out in the atmosphere. Strontium-90 can accumulate in living organisms and food chains, and because of its similarity chemical, can participate in carbonate equilibrium and replace calcium in various biological processes.
FIGUEIRA, R. Ç. L.; CUNHA, I. I. L. Contamination of the oceans by anthropogenic radionuclides. New Chemistry, no. 21, 1998 (adapted).
When entering a food chain of which man is a part, in which tissue of the human organism will strontium-90 be predominantly accumulated?
a) Cartilaginous.
b) Sanguine.
c) Muscle.
d) Nervous.
e) Bone.
Reply
Since strontium-90 has a chemical similarity to calcium in many biological processes, can even replace it in the composition of bones, the tissue with the highest calcium content that we have in the body human. Therefore, the template is the letter E.
question 2
(Unesp 2014)
Water collected in Fukushima in 2013 reveals record radioactivity
The company responsible for operating the Fukushima nuclear power plant, Tokyo Electric Power (Tepco), reported that water samples collected at the plant in July 2013 contained a record level of radioactivity, five times higher than originally detected. THE tepco explained that a new measurement revealed that the liquid, collected from an observation well between reactors 1 and 2 at the plant, contained a record level of the radioactive isotope strontium-90.
(www.folha.uol.com.br. Adapted.)
Strontium, due to its chemical behavior similar to that of calcium, can replace this in the teeth and bones of human beings. In the case of the radioactive isotope Sr-90, this substitution can be harmful to health. Consider the atomic numbers of Sr = 38 and Ca = 20. It is correct to state that the similarity of chemical behavior between calcium and strontium occurs because
a) have approximately the same atomic radius and, therefore, can be easily interchanged in the formation of compounds.
b) have the same number of electrons and, therefore, can be easily interchanged in the formation of compounds.
c) occupy the same group in the Periodic Classification, so they have the same number of valence electrons and form cations with the same charge.
d) are located in the same period as the Periodic Classification.
e) they are two representative metals and, therefore, have the same chemical properties.
Reply
Calcium and strontium are part of the same group of the periodic classification, having chemical similarity, consequence of having the same number of electrons in the valence shell and forming cations of the same charge. Thus, the template is the letter C.
The letter A is incorrect, as both do not have close atomic radii, since they are of different periods. The radius of strontium is significantly greater than that of calcium.
The letter B is incorrect, as both do not have the same number of electrons.
The letter D is incorrect, as both are not in the same period of the periodic classification, but in the same group.
The letter E is incorrect, because despite being representative metals, this does not guarantee that both have the same chemical properties.
By Stefano Araújo Novais
Chemistry teacher