Moscovium

Moscovium is the group 15 element below nitrogen, phosphorus, arsenic, antimony and bismuth. Of its three outer p electrons, two are predicted to fill the tightly held 7p1/2 sub-shell and one to sit alone in the higher-energy 7p3/2 orbital. That lone 7p3/2 electron should be easy to remove, so moscovium is predicted to form a stable +1 ion, Mc+, resembling the thallium(I) ion, unlike bismuth, which favors +3.

These predictions are largely untested. Moscovium-290, the longest-lived known isotope, has a half-life of under a second, and only around a hundred atoms have ever been detected. Gas-phase chemistry experiments have begun to probe its reactivity, but its chemical character is still mainly known from calculation. Its decay chains, running through nihonium and roentgenium down to dubnium, gave the first sightings of nihonium and of dubnium-268.

Discovery

A Dubna team led by Yuri Oganessian, in collaboration with Lawrence Livermore National Laboratory, bombarded americium-243 with calcium-48 in 2003 and reported four atoms of element 115 in 2004. The result was confirmed by later Dubna experiments and by GSI in 2012. IUPAC credited the collaboration in December 2015, and the name moscovium, after the Moscow Oblast region where Dubna lies, was approved in November 2016.