Roentgenium

At a glance

Symbol

Rg

Atomic number

111

Mass number of its longest-lived isotope

[282]

Group

11

Period

7

Family

transition metal

Electron configuration

[Rn] 5f¹⁴ 6d⁹ 7s² (predicted)

Electronegativity

not measured

On the table

Period 7, group 11. The other transition metals are tinted, and every cell opens its own article.

Electrons and bonding

Only a handful of atoms have ever been made, each lasting seconds or less, so its chemistry is predicted from its place in the table rather than measured.

Properties

State at 25 °C

not known

Physical properties

none measured; no more than a few atoms have ever existed at once

Where it is found

Not found in nature. It is made a few atoms at a time in particle accelerators by fusing lighter nuclei, and each atom decays within seconds to hours.

Discovery and name

Sigurd Hofmann's team at GSI made it in 1994 by fusing nickel and bismuth nuclei, weeks after darmstadtium. It was named in 2004 after Wilhelm Röntgen, who discovered X-rays in 1895.