Moscovium

Moscovium
Atomic number	115
Symbol	Mc
Group	15 (pnictogens)
Discovery	2003 (JINR & LLNL)
Electron configuration	[Rn] 5f14 6d10 7s2 7p3
Density	13.5 g/cm^3
Period	7
Main isotopes	287Mc, 288Mc, 289Mc
Phase STP	Solid
Block	p
Oxidation states	+1, +3
Wikidata	Q1303

Overview and key facts: Moscovium (symbol Mc) is a synthetic element with atomic number 115. It lies in group 15 (the pnictogen or nitrogen group) and period 7 of the periodic table, in the p-block. It is a transactinide and predicted to be a post-transition metal. Moscovium has no stable isotopes and does not occur naturally; it was first produced in 2003 by bombarding americium with calcium ions. Its most stable known isotope, ^290Mc, has a half-life of only about 0.65 seconds. Since only a few dozen atoms have ever been made experimentally, the element has no measured macroscopic properties. Calculations suggest that if a bulk sample did exist, moscovium would be a dense, soft metal (melting around 400 °C) resembling bismuth in some ways. Its predicted common oxidation states are +1 and +3 (with +5 being very unlikely), reflecting the so-called inert-pair effect for its 7s and 7p electrons. At standard conditions it would be a solid. In most periodic tables a temporary name ununpentium (Uup) was used until the official name moscovium was adopted by IUPAC in 2016, in honor of the Moscow (Dubna) research region.

Atomic structure and electron configuration: With 115 protons and 115 electrons, moscovium’s electron configuration is written [Rn] 5f¹⁴6d¹⁰7s²7p³. As a group-15 element, it nominally has five valence electrons (7s²7p³), but relativistic effects make two of the 7s and two of the 7p (specifically the 7p₁/₂) electrons relatively inert; only one 7p₃/₂ electron is readily available for bonding. This gives moscovium a strong inert-pair effect, much stronger than in bismuth. Chemically this means Mc^+ (the +1 ion, with configuration like flerovium) is relatively stable. The first ionization energy of moscovium is predicted to be about 5.6 eV, which follows the downward trend in group 15 (each heavier pnictogen has a lower ionization energy than the one above it). The atomic radius of moscovium is expected to be the largest in its group – theoretical estimates give a covalent radius around 157 pm (larger than bismuth’s) – reflecting its high atomic weight and the extended 7th shell. Its electronegativity would thus be low (lower than bismuth’s ~2.0 on the Pauling scale), meaning it only weakly attracts shared electrons in bonds. All in all, these atomic features suggest moscovium atoms would be large and very polarizable, with valence behavior dominated by that single 7p₃/₂ electron.

Isotopes and nuclear properties: Moscovium has no stable isotopes; all are highly radioactive. The known isotopes range from ^286Mc to ^290Mc (with neutron numbers 171 through 175). These have only been produced in particle accelerators, for example by the hot fusion reactions ^243Am + ^48Ca or ^249Bk + ^48Ca. Each of these heavy nuclei undergoes a rapid decay chain. All known moscovium isotopes decay primarily by emitting an alpha particle (a helium nucleus) to produce an isotope of element 113 (nihonium), which then further decays down a chain eventually reaching lighter nuclei (some of which undergo spontaneous fission). The decay energies in these alpha decays are typically around 10–11 MeV. Half-lives increase with neutron number: ^286Mc decays in milliseconds, ^287Mc in a few hundred milliseconds, and the longest-known ^290Mc lives about 0.65 seconds. No half-lives exceed a second. (In contrast, lighter α-emitters may decay in minutes or hours.) Nuclear spins and parity of moscovium isotopes have not been well established, as measurements are difficult with such short-lived nuclei. There is no practical use of moscovium for radioactivity-based dating or medicine – the lifetimes are too brief, and the element exists only in trace quantities for fundamental research. Scientists hope to reach more neutron-rich isotopes (like ^291–^293Mc) which theory predicts could lie near the hypothetical “island of stability” and perhaps have longer half-lives, but as of now such isotopes have not been observed.

Allotropes and typical compounds: No allotropes (different structural forms) of moscovium are known or expected, since only single atoms have ever been made. If it could form a bulk metal, it would likely adopt a close-packed metallic lattice (perhaps similar to the rhombohedral form of bismuth or the hexagonal close packing of thallium). In chemistry, moscovium’s behavior is almost entirely theoretical. By analogy with its lighter congeners, it should form a +3 oxide (sometimes written Mc₂O₃) and basic salts like a metallic symbol. However, because the +1 oxidation state is favored, its compounds are expected to resemble those of thallium(I) as much as bismuth(III). For example, predicted simple compounds include ionic salts like McCl, McBr, and McI (mcinlum(I) chloride, etc.), similar to TlCl. Thallium-like monovalent halides (McF, McCl, etc.) are expected to be molecular or ionic solids. Moscovium(III) halides (McCl₃, McBr₃, McI₃) should also exist in analogy to BiCl₃, but they would be easily hydrolyzed by water to give oxyhalides (such as McOCl) and hydroxides, just as bismuth(III) compounds do. A hydride McH₃ (“moscovine”) is predicted to be pyramidal (like NH₃, AsH₃, etc.), with a Mc–H bond length around 195 pm and H–Mc–H angle ~92°. All these compounds are only predicted by computer calculations; none have been isolated. In a recent gas-phase experiment, single atoms of moscovium were passed over a silica surface, and the weak adsorption measured confirmed that Mc is less chemically reactive than bismuth. In summary, any stable Mc compounds would be formed mainly in the +1 and +3 states, with bond types ranging from ionic (in +1 halides) to covalent/ionic (in +3 species), but with a general tendency toward the more electropositive (metallic) character.

Physical properties: Because it has never been produced in bulk, all physical properties of moscovium are extrapolated. Its predicted density is about 13.5 g/cm³ (placing it among the densest metals, on par with bismuth or mercury), reflecting its very heavy atomic mass. Calculations suggest a melting point around 400 °C and a boiling point near 1100 °C. These are relatively low for such a heavy element, implying relatively weak metallic bonds – comparable to those of thallium, which melts at 304 °C and boils at 1473 °C. The crystal structure is not known, but one might expect a close-packed lattice (face-centered cubic or hexagonal) typical of heavy metals. Moscovium would be a good conductor of heat and electricity, as all metals are expected to be, since it would have delocalized electrons in its metallic state. Its thermal conductivity and specific heat have not been calculated in detail, but are likely similar to bismuth or thallium. In terms of spectral properties, characteristic X-ray emission lines would exist (for example, Kα X-rays at very high energy corresponding to Z=115), but these have not been measured. Any small sample of moscovium would continually warm itself by its radioactivity (alpha decay heat), but in practice the number of atoms is too small for any bulk heating or toxicity under normal conditions.

Chemical reactivity and trends: Moscovium’s chemistry is strongly influenced by the relativistic stabilization of its inner electrons. As a result, it is expected to be less reactive (more inert) than bismuth. The favored Mc⁺ ion is analogous to Tl⁺, meaning Mc(I) chemistry would dominate in many environments. Moscovium would likely oxidize only very slowly in air, possibly forming a thin oxide film (like Tl and Bi do) if a sample could exist. It should dissolve in strong oxidizing acids to give Mc³⁺(aq) solutions (paralleling Bi(III) chemistry), while in neutral water a Mc(OH) interaction would hydrolyze due to the large charge and polarizability. Moscovium(III) would be a moderately strong oxidizing agent (as Bi(III) is), whereas Mc(I) would be relatively inert. Predicted trends down the pnictogens (N→Bi→Mc) suggest Mc will sit at the bottom: it has the lowest (most easily removed) ionization energy and the lowest electronegativity of its group. Experimental work supports its low reactivity: gas‐phase chromatography shows that single Mc atoms interact weakly with surfaces, weaker even than Bi. In summary, moscovium’s chemistry is expected to be dominated by +1 and +3 oxidation states; it should form ionic salts with halides and inert polar ligands, and it should not undergo unusual redox reactions beyond what a heavy post-transition metal does. It does not fit into any ordinary reactivity series, but if placed among metals it would be very low (close to thallium/bismuth).

Occurrence and production: Moscovium has no natural occurrence on Earth or in the solar system, because any primordial or cosmic-produced atoms would have decayed long ago. It is entirely man-made, produced only in specialized nuclear physics laboratories. The first synthesis (and most studies) have been done at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, often in collaboration with US scientists (Lawrence Livermore National Lab). Production involves heavy ion fusion: typically, a target of americium-243 or berkelium-249 is bombarded by a beam of calcium-48 ions. For example, ^243Am + ^48Ca → ^291Mc* (excited), which then sheds neutrons to form isotopes like ^288Mc, ^289Mc, etc. Other routes have been tested (e.g. plutonium or uranium targets with heavier projectiles). The reaction cross-sections are extremely small (on the order of picobarns), so the yield is very low: often only a few atoms over weeks of running the accelerator. No practical “refining” or large-scale production method exists beyond these collider experiments. No ores or mineral sources of moscovium are known. The main “producers” of moscovium today are therefore high-energy physics facilities: JINR’s GSI-Flerov Laboratory, and occasionally other heavy-ion labs that have the capability (for instance, the US DOE labs and research centers occasionally collaborate).

Applications and technology: There are no commercial or technological applications for moscovium, given its extreme scarcity and fleeting existence. Its only “use” is in basic scientific research. It helps physicists and chemists test models of nuclear structure (toward understanding the island of stability) and relativistic quantum chemistry (how superheavy elements behave). For example, the single-atom adsorption experiment mentioned earlier provided insight into the chemical periodicity at the bottom of the table. None of its isotopes is suitable for any practical purpose – their half-lives are far too short for any use in medicine, power generation, or electronics. If ever longer-lived isotopes were discovered, one could speculate about their potential roles (perhaps as a study of weak bonding extremes), but there is currently no conceivable application. In short, moscovium’s role is purely that of a research curiosity, symbolizing the frontier of the periodic table rather than any everyday technology. The global technology industry has no demand for element 115, and it plays no part in current materials science, catalysis, or energy.

Biology, environment, and safety: Moscovium has no biological role. On Earth, it is essentially non-existent outside labs, so it is not part of the environment or food chain. If a macroscopic quantity existed, it would be extremely toxic purely by its radioactivity (alpha decay is very damaging internally). In practice, any laboratory production yields only a handful of atoms, so radiological risk to humans is negligible beyond standard radiation safety protocols. Handling of moscovium (in theory) would require heavy shielding because even single atoms emit alpha particles and possibly neutrons (from spontaneous fission at the end of decay chains). The decay daughters (heavy bismuth, polonium, etc.) are themselves radioactive and hazardous. However, because only a few atoms exist at a time, there are no exposure limits or environmental regulations specific to moscovium; it is simply treated as a highly radioactive material. In other words, from a safety standpoint it is managed like any transuranic isotope in a nuclear lab: remote handling, containment, and decay monitoring. There is no chemical toxicity data (it would likely be a heavy-metal poison if it could be ingested), and normal precautions for radioisotopes apply. It poses no environmental problem outside the research context, as it decays away almost immediately if produced.

History and etymology: Moscovium was first synthesized in 2003–2004 at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, by a team led by Yuri Oganessian working with Lawrence Livermore National Laboratory. They achieved element 115 by bombarding an americium-243 target with calcium-48 nuclei. The earliest results, reported in 2004, identified two atoms of ^288Mc and one of ^287Mc, observed via their characteristic alpha-decay chains leading eventually to known isotopes of dubnium. Confirmation came through repeat experiments (for example in 2009) and cross-reactions that produced the isotope ^289Mc, verifying the earlier observations. Throughout the late 2000s, more isotopes (^289Mc, ^290Mc) were made at Dubna and in collaborations, and data from decays were collected. Initially, a systematic provisional name “ununpentium” (Latin for 115) was used, following IUPAC’s rules. After much deliberation, the discovery was officially recognized in late 2015 by the IUPAC/IUPAP Joint Working Party, giving credit to the Dubna–Livermore team. In November 2016, element 115 was formally named moscovium (Mc) after Moscow Oblast (the Moscow region), to honor the region where Dubna is located. The symbol Mc was simultaneously adopted. The name reflects the tradition of honoring places or scientists of element discovery (similar to dubnium, americium, etc.). Since moscovium’s discovery, the name has been widely accepted and appears in all updated periodic tables. There are no significant cultural or industrial milestones involving moscovium beyond its role in expanding the periodic table. Its discovery is part of the larger scientific effort in superheavy elements, and its naming honors the geographic home of its pioneers.

Data Table

Property	Value
Symbol	Mc
Atomic number (Z)	115
Atomic weight	— (no stable isotopes; longest-lived isotope ^290Mc ~290 u)
Group/period/block	15 (pnictogen) / 7 / p-block
Category	Post-transition metal (predicted)
Electron configuration	[Rn] 5f^14 6d^10 7s^2 7p^3
Oxidation states	+1, +3 (predicted; +5 unlikely)
Crystal structure	— (predicted close-packed metal lattice)
Density (predicted)	~13.5 g·cm^−3
Melting point (predicted)	~400 °C
Boiling point (predicted)	~1100 °C
First ionization energy (predicted)	~5.58 eV
Longest-lived isotope	^290Mc, t_1/2 ≈ 0.65 s
Discovery	2003 (Dubna, Russia, Oganessian et al.)
Etymology	Named for Moscow Oblast, Russia (2016)