In 1861, the recently invented physical method for studying substances - spectral analysis - once again demonstrated its power and reliability, as a guarantee of a great future in science and technology. With its help, the second previously unknown chemical element, rubidium, was discovered. Then, with the discovery of the periodic law by D. I. Mendeleev in 1869, rubidium, along with other elements, took its place in the table, which brought order to chemical science.
Further study of rubidium showed that this element has a number of interesting and valuable properties. We will consider here the most characteristic and important of them.
General characteristics of a chemical element
Rubidium has an atomic number of 37, that is, in its atoms, the composition of the nuclei includes just such a number of positively charged particles - protons. Respectivelya neutral atom has 37 electrons.
Element symbol - Rb. In the periodic system, rubidium is classified as an element of group I, the period is fifth (in the short-period version of the table, it belongs to the main subgroup of group I and is located in the sixth row). It is an alkali metal, is a soft, very fusible, silver-white crystalline substance.
Discovery history
The honor of discovering the chemical element rubidium belongs to two German scientists - chemist Robert Bunsen and physicist Gustav Kirchhoff, the authors of the spectroscopic method for studying the composition of matter. After the use of spectral analysis led to the discovery of cesium in 1860, the scientists continued their research, and the very next year, when studying the spectrum of the mineral lepidolite, they discovered two unidentified dark red lines. It is thanks to the characteristic shade of the strongest spectral lines, by which it was possible to establish the existence of a previously unknown element, that it got its name: the word rubidus is translated from Latin as “crimson, dark red.”
In 1863, Bunsen was the first to isolate metallic rubidium from mineral spring water by evaporating a large amount of solution, separating potassium, cesium and rubidium s alts, and finally reducing the metal using soot. Later, N. Beketov managed to recover rubidium from its hydroxide using aluminum powder.
Physical characteristic of the element
Rubidium is a light metal, it hasdensity 1.53g/cm3 (at zero temperature). Forms crystals with a cubic body-centered lattice. Rubidium melts at only 39 °C, that is, at room temperature, its consistency is already close to pasty. The metal boils at 687 °C and its vapors are greenish-blue.
Rubidium is a paramagnet. In terms of conductivity, it is more than 8 times superior to mercury at 0 ° C and is almost as many times inferior to silver. Like other alkali metals, rubidium has a very low photoelectric effect threshold. To excite a photocurrent, long-wavelength (that is, low-frequency and carrying less energy) red light rays are sufficient in it. In this respect, only cesium surpasses it in sensitivity.
Isotopes
Rubidium has an atomic weight of 85.468. It occurs in nature in the form of two isotopes that differ in the number of neutrons in the nucleus: rubidium-85 makes up the largest proportion (72.2%), and in a much smaller amount - 27.8% - rubidium-87. The nuclei of their atoms, in addition to 37 protons, contain 48 and 50 neutrons, respectively. The lighter isotope is stable, while rubidium-87 has a huge half-life of 49 billion years.
At present, several dozens of radioactive isotopes of this chemical element have been artificially obtained: from ultralight rubidium-71 to rubidium-102 overloaded with neutrons. The half-lives of artificial isotopes range from a few months to 30 nanoseconds.
Basic chemical properties
As noted above, in a series of chemical elements, rubidium (like sodium, potassium, lithium, cesium and francium) belongs to alkali metals. The peculiarity of the electronic configuration of their atoms, which determines the chemical properties, is the presence of only one electron at the external energy level. This electron easily leaves the atom, and the metal ion at the same time acquires an energetically favorable electronic configuration of the inert element in front of it in the periodic table. For rubidium, this is the krypton configuration.
Thus, rubidium, like other alkali metals, has pronounced reducing properties and an oxidation state of +1. Alkaline properties are more pronounced with increasing atomic weight, since the radius of the atom also increases, and, accordingly, the bond between the outer electron and the nucleus is weakened, which leads to an increase in chemical activity. Therefore, rubidium is more active than lithium, sodium and potassium, and cesium, in turn, is more active than rubidium.
Summing up all the above about rubidium, the element can be parsed, as in the illustration below.
Compounds formed by rubidium
In air, this metal, due to its exceptional reactivity, oxidizes violently, with ignition (the flame has a violet-pinkish color); during the reaction, superoxide and rubidium peroxide are formed, exhibiting the properties of strong oxidizing agents:
- Rb + O2 → RbO2.
- 2Rb + O2 →Rb2O2.
Oxide is formed if the access of oxygen to the reaction is limited:
- 4Rb + O2 → 2Rb2O.
This is a yellow substance that reacts with water, acids and acid oxides. In the first case, one of the strongest alkalis is formed - rubidium hydroxide, in the rest - s alts, for example, rubidium sulfate Rb2SO4, most of which are soluble.
Even more violently, accompanied by an explosion (since both rubidium and the released hydrogen instantly ignite), the metal reacts with water, which forms rubidium hydroxide, an extremely aggressive compound:
- 2Rb + 2H2O → 2RbOH +H2.
Rubidium is a chemical element that can also directly react with many non-metals - with phosphorus, hydrogen, carbon, silicon, and halogens. Rubidium halides - RbF, RbCl, RbBr, RbI - are readily soluble in water and in some organic solvents, such as ethanol or formic acid. The interaction of metal with sulfur (rubbing with sulfur powder) occurs explosively and leads to the formation of sulfide.
There are also poorly soluble compounds of rubidium, such as perchlorate RbClO4, they are used in analytics to determine this chemical element.
Being in nature
Rubidium is not a rare element. It is found almost everywhere, included inthe composition of many minerals and rocks, and is also contained in the ocean, in underground and river waters. In the earth's crust, the content of rubidium reaches the total value of the content of copper, zinc and nickel. However, unlike many much rarer metals, rubidium is an extremely trace element, its concentration in the rock is very low, and it does not form its own minerals.
In the composition of minerals, rubidium accompanies potassium everywhere. The highest concentration of rubidium is found in lepidolites, minerals that also serve as a source of lithium and cesium. So rubidium is always present in small amounts where other alkali metals are found.
A little about the use of rubidium
Brief description of chem. rubidium element can be supplemented with a few words about the areas in which this metal and its compounds are used.
Rubidium is used in the production of photocells, in laser technology, is part of some special alloys for rocket technology. In the chemical industry, rubidium s alts are used due to their high catalytic activity. One of the artificial isotopes, rubidium-86, is used in gamma-ray flaw detection and, in addition, in the pharmaceutical industry for the sterilization of drugs.
Another isotope, rubidium-87, is used in geochronology, where it is used to determine the age of the oldest rocks due to its very long half-life (rubidium-strontium method).
If several decadesIn the past, it was thought that rubidium was a chemical element, the scope of which is unlikely to expand, but at present, new prospects for this metal are emerging, for example, in catalysis, in high-temperature turbine units, in special optics and in other areas. So rubidium plays and will continue to play an important role in modern technologies.
