THE ruthenium, atomic number 44, is a metal located in group 8 of the Periodic Table. It is part of what we know as the Platinum Group Metals, along with osmium, palladium, iridium, rhodium and, of course, the platinum. It is capable of having several oxidation states, even reaching a formal charge of +8, the highest in the Periodic Table.
Due to its nobility, ruthenium has good physicochemical properties, such as low reactivity and broad resistance to corrosion. Therefore, it is used in metal alloys to increase its mechanical properties and also improve its anticorrosion protection. In addition, ruthenium and its compounds have been used in modern chemical reactions and in the development of cheaper solar cells.
See too: Zirconium — the chemically similar element to hafnium
Summary on ruthenium
Ruthenium is a metal belonging to group 8 of Periodic table.
It is one of the Platinum Group Metals (MGP), which also include palladium, osmium, iridium, rhodium and platinum itself.
It is little present in Earth's crust, but because of its low reactivity, it can be found in its pure form.
It is capable of producing compounds with different oxidation states, which range from 0 to +8.
It is obtained commercially as a by-product of mining nickel.
In the metallurgical industry, it improves the physical and anti-corrosion capacity of some alloys.
Its compounds have been used in modern chemical processes and in the manufacture of cheaper than traditional solar cells.
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Ruthenium properties
Symbol: Ru.
Atomic number: 44.
Atomic mass: 101.07 c.u.
Electronegativity: 2,2.
Fusion point: 2334°C.
Boiling point: 4150°C.
Density: 12.1 g.cm-3 (at 20°C).
Electronic configuration: [Kr] 5s1 4d7.
Chemical Series: group 8, transition metals, platinum group metals.
characteristics of ruthenium
Ruthenium is one of the metals belonging to the group known as Platinum Group Metals (MGP), also composed of platinum, palladium, osmium, iridium and rhodium metals. As it belongs to this group, ruthenium has some characteristics that refer to the noble metals, Like yours low reactivity and high corrosion resistance.
It is a metal not present in the earth's crust, with an average composition of 10-8% in large scale. However, it is more present in meteorites, as in chondrites and meteorites of iron. Ruthenium has seven natural isotopes and 34 radioactive isotopes.
In its metallic form, ruthenium is protected by a thin layer of RuO2, which prevents the oxidation of this metal by the O2 up to a temperature of 870 K. Ruthenium can still react with fluorine (F2) and chlorine (Cl2) under heating and is also attacked by hydrochloric acid when it is mixed with other oxidizing agents such as KClO4, resulting in explosive oxidation.
Molten alkaline substances also have the ability to react with the metal. However, he is not attacked by acids, being in low or high temperature, and cannot be attacked by the aqua regia.
One of the characteristics of ruthenium, which extends to osmium (an element also of group 8), is the wide variety of oxidation states that this element can have: the NOx of its compounds can vary from 0 to +8, with the +3 state being the most stable.
The +8 oxidation state, inclusive, is the highest reached by any element in the Periodic Table. An example of a substance with this NOx is RuO4. This oxide is toxic, with an odor reminiscent of ozone, very soluble in carbon tetrachloride (CCl4). It is also a powerful oxidant.
Read too: Chromium — the chemical element used in stainless steel for its anti-corrosion properties
Where can ruthenium be found?
Because of its noble characteristic, ruthenium can be found in its native form in nature, together with the other MGPs, as in the Ural Mountains and in regions of North and South America.
However, commercially it is most commonly obtained through nickel tailings, originating from its refining coming from the pentlandite ore, (Fe, Ni) S. Of note are the deposits of South Africa, Russia, Zimbabwe, U.S and Canada.
Obtaining ruthenium
Noble metals are difficult to isolate.In the case of MGPs, the difficulty arises because their physicochemical properties are similar to a certain extent. Extraction of ruthenium is quite complex, although there are many techniques available. In a way, the problem is to find a safe technique that can be applied in an industrial reality, and not just in the laboratory.
For example, the distillation of ruthenium tetroxide, RuO4, can be made in the laboratory and it would be interesting to separate it from other MGPs, as it is a volatile compound. However, its application on a large scale is not recommended, since above 180 °C ruthenium tetroxide is explosive. It is also difficult to obtain it by precipitation, as the chemical similarity with the other MGPs makes selective precipitation difficult.
So, the most used way is via solvent extraction, in which ruthenium can be concentrated and separated from the other compounds. One of the methods is its conversion to the soluble species RuCl62-, which can be separated with tertiary amines and, consequently, produce a ruthenium of purity above 99%.
applications of ruthenium
In the industry, the application of ruthenium in metallic alloys is very well seen, since improves the physicochemical properties of the product. For example, adding 0.1% by mass of ruthenium to titanium makes its corrosion resistance increase 100 times.
However, a good part of the ruthenium is applied in studies and in the development of its products. Studies involving catalysts based on ruthenium integrated the metathesis technique in organic synthesis, responsible for laureate Yves Chauvin, Robert Grubbs and Richard Schrock with the Nobel Prize in Chemistry in 2005.
Ruthenium complexes have also been extensively employed in catalytic hydrogenation reactions. asymmetric, which won William Knowles, Barry Sharpless and Ryoji Noyori the Nobel Prize in Chemistry for 2001.
An extensively studied ruthenium compound is the complex of this metal with 2,2'-bipyridine, the so-called ruby. It was noticed that this substance and some derivatives had great oxidation capacity, due to Ru3+, and reduction, because of bipyridine. Ruthenium compounds have also been studied for the development of lower cost solar cells compared to those on the market.
Know more:Vanadium — an important catalyst for the chemical industry
history of ruthenium
In 1827, Jakob Berzelius and Gottfried Osann examined the residues left over from the dissolution of platinum from the Ural Mountains with aqua regia. While Berzelius found no new metals, Osann believed he had found three new metals and for one of them he named ruthenium.
Karl Karlovitch Klaus is commonly considered the discoverer of ruthenium. In 1844, he demonstrated that the compound observed by Osann consisted of a oxide ruthenium impure. Klaus obtained about 6 g of the metal from insoluble platinum waste treated with aqua regia.
The name Ruthenia is a tribute to Russia — the country's Latin name is Ruthenia. Klaus kept the name in recognition of Osann's work, but also in honor of his homeland.
Exercises solved on ruthenium
question 1
Ruthenium is a metal that has several possible oxidation states, ranging from 0 to +8. in Ru oxides2THE3, RuO2 and RuO4, what are the oxidation numbers of ruthenium, respectively?
A) 0, +2 and +4
B) +3, +2 and +4
C) +3, +4 and +8
D) +2, +4 and +5
E) 0, +4 and +8
Resolution:
Alternative C
In the oxides, the oxygen keeps NOx equal to -2. Thus, we can calculate the NOx of ruthenium in the compounds as follows:
Ru2THE3: 2x + 3(-2) = 0 → 2x – 6 = 0 → 2x = 6 → x = 3
RuO2: y + 2(-2) = 0 → y – 4 = 0 → y = 4
RuO4: z + 4(-2) = 0 → z – 8 = 0 → z = 8
question 2
Ruthenium is capable of forming the oxide RuO4, a compound in which the element has the highest possible charge (NOx) for an element in the Periodic Table. About this compound, we can say that:
A) It is a neutral oxide.
B) It is an oxidizing substance.
C) The NOx of ruthenium in this compound is +4.
D) It is a reducing substance.
Resolution:
Alternative B
in the RuO4, the NOx of ruthenium is +8. In this case, in a chemical reaction, its charge could not increase, as it has already reached the maximum value (which is even the largest possible for the Periodic Table). Thus, in a chemical process, the NOx of Ru can only fall, that is, the ruthenium can only be reduced.
When ruthenium is reduced, it oxidizes another substance that is in the reaction medium, causing this substance to be characterized as an oxidant.
By Stefano Araújo Novais
Chemistry teacher
