Roentgenium

Named after Wilhelm Röntgen, who discovered X-rays, and expected to be a very heavy relative of gold.

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

Roentgenium has 111 electrons, one for every proton, so the atom carries no charge. Below are the same 111 electrons written two ways.

Simple form: electrons per shell

shell 12shell 28shell 318shell 432shell 532shell 617shell 72

Counting outward from the nucleus: 2, 8, 18, 32, 32, 17, 2. The outer shell is picked out.

Orbital form: electrons per subshell

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d⁹ 7s²

Short form: [Rn] 5f¹⁴ 6d⁹ 7s², where [Rn] stands for the 86 electrons radon already has.

That list runs by shell. In the order the subshells fill it reads [Rn] 7s² 5f¹⁴ 6d⁹, because a subshell fills by its energy, not by its shell number.

5f¹⁴↑↓↑↓↑↓↑↓↑↓↑↓↑↓

6d⁹↑↓↑↓↑↓↑↓↑

7s²↑↓

The boxes hold the electrons beyond [Rn]. Each box is one orbital and takes two electrons at most, spinning opposite ways. They spread out singly before they pair up.

How to read the two

The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 4 here is 4s² 4p⁶ 4d¹⁰ 4f¹⁴, and 2 + 6 + 10 + 14 is 32.

Roentgenium sits in period 7 and has 7 shells. The period number counts the shells.

No one has measured this configuration. Only a few atoms of roentgenium have ever existed, so it is predicted from the pattern of the table.

What that means for bonding

The outer shell holds 2 electrons. Those are the ones roentgenium can lose, gain or share, so they are the ones that decide what it bonds with.

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.

What it is used for

Research only; its chemistry has not been studied.