The 115th element of the periodic table - Moscow (moscovium) - is an extra heavy synthetic element with the symbol Mc and atomic number 115. It was first obtained in 2003 by a joint team of Russian and American scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. In December 2015, it was recognized as one of four new elements by the Joint Working Group of International Scientific Organizations IUPAC / IUPAP. On November 28, 2016, it was officially named after the Moscow region, where JINR is located.
Characteristic
The 115th element of the periodic table is an extremely radioactive substance: its most stable known isotope, moscovium-290, has a half-life of only 0.8 seconds. Scientists attribute Muscovy to intransitive metals, in a number of characteristics similar to bismuth. The periodic table refers to the transactinide elements of the p-block of the 7th period and is placed in group 15 as the heaviest pnictogen (an element of the nitrogen subgroup), although it is not confirmed that it behaves like a heavier bismuth homolog.
According to calculations, the element has some properties similar to the lighter homologues: nitrogen, phosphorus, arsenic, antimony, and bismuth. At the same time, it demonstrates several significant differences from them. To date, about 100 Moscow atoms have been synthesized, which have mass numbers from 287 to 290.
Physical properties
Valence electrons of 115 elements of the periodic table are divided into three subshells: 7s (two electrons), 7p 1/2 (two electrons) and 7p 3/2 (one electron). The first two of them are relativistically stabilized and, therefore, behave like inert gases, while the last two are relativistically destabilized and can easily participate in chemical interactions. Thus, the primary ionization potential of Muscovy should be about 5.58 eV. According to calculations, moscovium should be a dense metal due to its high atomic weight with a density of about 13.5 g / cm 3 .
Estimated design characteristics:
- Phase: solid.
- Melting point: 400 ° C (670 ° K, 750 ° F).
- Boiling point: 1100 ° C (1400 ° K, 2000 ° F).
- Specific heat of fusion: 5.90-5.98 kJ / mol.
- Specific heat of vaporization and condensation: 138 kJ / mol.
Chemical properties
The 115th element of the periodic table is the third in the series of chemical elements 7p and is the heaviest member of group 15 in the periodic table, located below bismuth. The chemical interaction of Muscovy in an aqueous solution is due to the characteristics of Mc + and Mc 3+ ions. The former, presumably, are easily hydrolyzed and form an ionic bond with halogens, cyanides, and ammonia. Muscovy (I) hydroxide (McOH), carbonate (Mc 2 CO 3 ), oxalate (Mc 2 C 2 O 4 ) and fluoride (McF) must be dissolved in water. Sulfide (Ms 2 S) must be insoluble. Chloride (McCl), bromide (McBr), iodide (McI) and thiocyanate (McSCN) are poorly soluble compounds.
Muscovy (III) fluoride (McF 3 ) and thiosonide (McS 3 ) are supposedly insoluble in water (similar to the corresponding bismuth compounds). While chloride (III) (McCl 3 ), bromide (McBr 3 ) and iodide (McI 3 ) should be readily soluble and easily hydrolyzed to form oxohalides such as McOCl and McOBr (also similar to bismuth). Muscovy (I) and (III) oxides have similar oxidation states, and their relative stability largely depends on which elements they interact with.
Uncertainty
Due to the fact that the 115th element of the periodic table is synthesized by single atoms, it is problematic to determine experimentally its exact characteristics. Scientists have to rely on theoretical calculations and compare with more stable elements with similar properties.
In 2011, experiments were conducted to create nichonium, flerovium, and Muscovite isotopes in reactions between “accelerators” (calcium-48) and “targets” (americium-243 and plutonium-244) to study their properties. However, the “targets” included impurities of lead and bismuth and, therefore, some isotopes of bismuth and polonium were obtained in nucleon transfer reactions, which complicated the experiment. Meanwhile, the obtained data will help scientists in more detail study the heavy homologues of bismuth and polonium, such as moscovium and livermorium.
Opening
The first successful synthesis of 115 elements of the periodic table was the joint work of Russian and American scientists in August 2003 at JINR in Dubna. The team, led by nuclear physicist Yuri Hovhannisyan, in addition to domestic specialists, included colleagues from Lawrence Livermore National Laboratory. On February 2, 2004, researchers published in the Physical Review that they bombarded americium-243 with calcium-48 ions at the U-400 cyclotron and received four atoms of the new substance (one nucleus 287 Mc and three nuclei 288 Mc). These atoms decay (decay) due to the emission of alpha particles to the nichonium element in about 100 milliseconds. Two heavier isotopes of Muscovy, 289 Mc and 290 Mc, were discovered in 2009-2010.
Initially, IUPAC could not approve the discovery of a new item. Confirmation from other sources was required. Over the next few years, another evaluation of later experiments was carried out, and once again the statement of the Dubna team to open the 115th element was put forward.
In August 2013, a group of researchers from the University of Lund and the Institute of Heavy Ions in Darmstadt (Germany) announced that they repeated the 2004 experiment, confirming the results obtained in Dubna. Another confirmation was published by a team of scientists who worked at Berkeley in 2015. In December 2015, the IUPAC / IUPAP joint working group recognized the discovery of this element and gave priority to the opening of the Russian-American team of researchers.
Title
115 element of the periodic table in 1979, in accordance with the IUPAC recommendation, it was decided to call “ununpent” and designate it with the corresponding UUP symbol. Despite the fact that this name has since been widely used in relation to an undiscovered (but theoretically predicted) element, it has not taken root in the community of physicists. Most often, the substance was called that - element No. 115 or E115.
On December 30, 2015, the discovery of a new element was recognized by the International Union of Pure and Applied Chemistry. Under the new rules, discoverers have the right to propose their own name for a new substance. At first it was supposed to name the 115th element of the periodic table "langevinium" in honor of the physicist Paul Langevin. Later, a team of scientists from Dubna, as an option, proposed the name "Muscovy" in honor of the Moscow region, where the discovery was made. In June 2016, IUPAC approved the initiative and on November 28, 2016 officially approved the name “moscovium”.