Which element has the chemical symbol Re?



properties
Generally
Name, symbol, atomic number Rhenium, Re, 75
seriesTransition metals
Group, period, block7, 6, d
Look grayish white
Mass fraction of the earth's envelope 1 · 10-7 %
Atomic
Atomic mass 186.207 u
Atomic radius (calculated) 135 (188) pm
Covalent radius 159 pm
Van der Waals radius - pm
Electron configuration [Xe] 4f145d56s2
Electrons per energy level 2, 8, 18, 32, 13, 2
1. Ionization energy 760 kJ / mol
2. Ionization energy 1260 kJ / mol
3. Ionization energy 2510 kJ / mol
4. Ionization energy 3640 kJ / mol
Physically
Physical state firmly
Modifications
Crystal structure hexagonal
density 21.03 g / cm3
magnetism
Melting point 3459 K (3186 ° C)
boiling point 5869 K (5596 ° C)
Molar volume 8,86 · 10-6 m3/ mol
Heat of evaporation 715 kJ / mol
Heat of fusion 33.2 kJ / mol
Vapor pressure

3.24 Pa at 3453 K.

Speed ​​of sound 4700 m / s at 293.15 K.
Specific heat capacity 137 J / (kg K)
Electric conductivity 5,42 · 106S / m
Thermal conductivity 47.9 W / (m K)
Chemically
Oxidation states -2, 2, 4, 6, 7
Oxides (basicity) (slightly angry)
Normal potential -0.251 V (ReO2 + 4H+ + 4e-
→ Re + 2H2O)
Electronegativity 1.9 (Pauling scale)
Isotopes
isotopeNHt1/2ZMZE MeVZP
185re

37,4 %

Stable
186re

{syn.}

89.25 hβ1,069186Os
ε0,582186W.
186mre

{syn.}

200,000 aIT0,149186re
β1,218186Os
187re

62,6 %

4,12 · 1010aβ0,003187Os
NMR properties
  Spinγ in
rad · T−1· S−1
E. fL. at
W = 4.7 T
in MHz
185re 5/2 6,084 · 107 0,137 45
187re5/2 6,023 · 1070,133 45,5
safety instructions
Hazardous substance labeling
powder
[1]
R and S phrases R: 11[1] (Powder)
S: 16[1](Powder)
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions.

rhenium is a chemical element with the symbol Re and the atomic number 75. In the periodic table of the elements it is in the 7th group or manganese group. It is a rare, silver-white, shiny, heavy transition metal. It is used as an alloy component, in thermocouples and as a catalyst in gasoline production. Biological functions are not known, it does not normally occur in the human organism and it is not toxic.

history

The existence of the later rhenium was first established in 1871[2] predicted by Dmitri Ivanovich Mendeleev as Dwi-Mangan. From the regularities of the periodic table he designed, he concluded that below manganese there must be two as yet unknown elements, the later technetium and rhenium.

Rhenium was only discovered in 1925 by Walter Noddack, Ida Tacke and Otto Berg. They examined columbite to find the elements they were looking for, Eka and Dwi manganese. Since the elements sought are only contained in it on a very small scale, they had to be enriched by separating the others. Finally, the later rhenium could be detected by X-ray spectroscopy.[3] Noddack and Tacke also claimed to have found very small amounts of the later technetium, but this could not be confirmed by representation of the element. They named the elements rhenium (lat. Rhenus for Rhine) and Masurium (from Masuria). However, this name did not establish itself after the final discovery of technetium in 1937.

In 1928, Noddack and Tacke were able to extract one gram of rhenium from 660 kilograms of molybdenum ore for the first time.[4] Because of the high costs, the production of significant quantities did not begin until 1950, when there was a greater demand for developed tungsten-rhenium and molybdenum-rhenium alloys.

Occurrence

Along with rhodium, ruthenium and osmium, rhenium is one of the rarest stable elements on earth. Its share in the earth's crust is only 0.4 ppb[5]. It does not occur naturally, but is exclusively bound in some ores. Since rhenium has properties similar to molybdenum, it is mainly found in molybdenum ores such as molybdenum luster MoS2. They can contain up to 0.2%[6] Rhenium may be included. Further minerals containing rhenium are columbite (Fe, Mn) [NbO3], Gadolinite Y2 Fe Be [O | SiO4]2 and Alvit ZrSiO4. Major deposits are in the United States, Canada, and Chile. The Mansfeld copper slate also contains small amounts of rhenium.

So far, only one rhenium mineral, rheniite (rhenium (IV) sulfide, ReS2) discovered. It was found at the summit crater of the Kudriavy volcano on the Iturup island of the Kuriles (Russia).[7]

Extraction and presentation

The basic material for the extraction of rhenium are molybdenum ores, especially molybdenum luster. If these are roasted in the course of molybdenum extraction, rhenium accumulates as volatile rhenium (VII) oxide in the fly ash. If the enriched rhenium (VII) oxide is reacted with ammonia-containing water, ammonium perrhenate (NH4ReO4).

At high temperatures, this is reduced to elemental rhenium with hydrogen.

The main producers in 2006 were Chile, Kazakhstan and the United States, the total amount of rhenium produced was about 45 tons.[8]

properties

Physical Properties

Rhenium is a shiny white hard heavy metal that looks similar to palladium and platinum. It crystallizes in a hexagonal close packing of spheres. The density of rhenium 21.03 g / cm3[10] is only surpassed by the three platinum metals osmium, iridium and platinum.

Rhenium is one of the elements with the highest melting points. With 3186 ° C[11] it is only supported by the highest melting metal tungsten (3387 ° C[11]) and carbon.

Rhenium can be easily processed by forging and welding because it is ductile and, unlike tungsten or molybdenum, remains this even after recrystallization. When welding rhenium, there is also no embrittlement, which would lead to greater brittleness and thus poorer material properties.[12]

Chemical compounds

Although rhenium with a negative standard potential is not a noble metal, it is unreactive at room temperature and stable to air. It only reacts when heated above 400 ° C[10] with oxygen to form rhenium (VII) oxide. It also reacts with the non-metals fluorine, chlorine and sulfur when heated.

Rhenium is not soluble in non-oxidizing acids such as hydrochloric acid or hydrofluoric acid. In contrast, the oxidizing sulfuric and nitric acids readily dissolve rhenium. Rhenates of the form RhO are easily formed with oxidative melts4-.

Isotopes

A total of 34 isotopes and a further 20 core isomers of rhenium are known.[13] Of these, two come, the isotopes 185Re and 187Re of course before. 185Re, with a share of 37.40%[13] occurs in the natural isotope distribution is the only stable isotope. That with a share of 62.60%[13] more frequent 187Re is weakly radioactive. It disintegrates with beta decay with a half-life of 4.12 · 1010[13] Years to 187