About

Roentgenium is a synthetic element named in honor of Wilhelm Conrad Röntgen, the German physicist who discovered X-rays. It is extremely unstable, and its most stable known isotope has a half-life of about 26 seconds. It is predicted to be a very heavy, noble metal similar to gold. All that is known about it comes from theoretical calculations and the properties of lighter homologs.

Atomic Properties

Atomic Number111

Atomic Weight282.169 u

Neutrons (common)171

Electron Configuration[Rn] 5f¹⁴ 6d¹⁰ 7s¹

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 5f¹⁴ 6d¹⁰ 7s¹

Electrons per Shell2, 8, 18, 32, 32, 18, 1

Electron Affinity151 kJ/mol

Oxidation States+5, +3, +1

Covalent Radius141 pm

Periodic Table Position

Group11

Period7

BlockD

Chemical SeriesTransition metals

Physical Properties

State at STPsolid

Crystal Structurebcc

Magnetic Orderingparamagnetic

Discovery

Discovered byGesellschaft für Schwerionenforschung

Discovery Year1,994

Occurrencesynthetic

CAS Number54386-24-2

Electron Configuration

Energy

↿⇂

1s

↿⇂

2s

↿⇂

2p

↿⇂

3s

↿⇂

3p

↿⇂

4s

↿⇂

3d

↿⇂

4p

↿⇂

5s

↿⇂

4d

↿⇂

5p

↿⇂

6s

↿⇂

4f

↿⇂

5d

↿⇂

6p

↿

7s

↿⇂

5f

↿⇂

6d

7p

Isotopes of Roentgenium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
²⁸¹Rg	281.166160	—	19 s	Alpha Decay