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What is Roentgenium?

Roentgenium can be described as a chemical element having the symbol Rg with an atomic number 111. It is said to be an extremely radioactive synthetic element that can be made in a laboratory but cannot be found in nature. One of the most stable well-known isotopes, named roentgenium-282, contains a half-life of 100 seconds, although the roentgenium-286, which is unconfirmed, can contain a longer half-life of about 10.7 minutes. Firstly, Roentgenium was created in 1994 by the centre named GSI Helmholtz Centre for the Heavy Ion Research, located near Darmstadt, in Germany. It was named after the famous physicist Wilhelm Röntgen (also named Roentgen), who discovered the medical X-rays.

About Roentgenium

Roentgenium is a d-block transactinide element in the periodic table. It is placed in the group 11 elements and is a member of the 7th period. However, no chemical experiments have been carried out to confirm that it behaves as a heavier homologue to gold in group 11 as the 9th member of the transition metal's 6d series. The roentgenium element is also calculated to contain similar properties to its lighter copper, homologues, gold, and silver, although it can represent a few differences from them.

Properties of Roentgenium

  • This element contains around 7 isotopes whose half-lives are known, with the mass numbers ranging from 272 to 282.

  • The element contains a metallic gold (otherwise yellow solid) appearance.

  • This element undergoes decay under the process of spontaneous fission.

  • An isotope of this element (called 218Rg) contains a half-life of 26 seconds.

Let us look at the physical and chemical properties of Roentgenium.

Physical Properties of Roentgenium

Atomic Number




Atomic Mass

280 amu

Discovered by

Gottfried Münzenberg and Peter Armbruster, in 1994

Chemical Properties of Roentgenium





Atomic Number




State at 20°C


Key isotopes


Electron configuration

[Rn] 5f146d107s1

Relative atomic mass


CAS number



Using the nomenclature invented by Mendeleev for the undiscovered and unnamed elements, Roentgenium is called eka-gold. IUPAC published the recommendations in 1979. The element was referred to as unununium (having the corresponding symbol - Uuu), which has a systematic element name as a placeholder until the element was discovered. A permanent name was decided. Although it can be widely used in the chemical community on every level, ranging from the chemistry classrooms to advanced textbooks, the recommendations were mostly ignored by the scientists in the same field. They called it element 111, having the symbol of E111 (111) or only as 111.

In 2004, the term roentgenium (Rg) was suggested by the GSI team to honour one of the German physicist Wilhelm Conrad Röntgen, who was the discoverer of X-rays. IUPAC accepted this name on November 1, 2004.

Facts About Roentgenium

  • This element was named after Wilhelm Röntgen, who is the founder of X-rays.

  • For the first time, it was synthesized by Sigurd and Hofmann at the Institute for Heavy Ion Research, located in Germany in 1994.

  • This element is also artificially formed by bismuth ions bombarding with the nickel ions in a linear accelerator.


Roentgenium contains isotopes that are zero stable or naturally occurring. Many of the radioactive isotopes have been synthesized in the chemical laboratory, either as intermediate decay products of heavier elements or by the fusion of nuclei of lighter elements. Nine separate roentgenium isotopes have been identified with atomic masses of 272, 274, 278-283, and finally 286 (where 283, 286 are unconfirmed), and two of them, roentgenium-272 and 274, have been known, although they are unconfirmed metastable states. All these decay via spontaneous fission or alpha decay, though 280Rg can also contain an electron capture branch.

Stability and Half-lives

All the roentgenium isotopes are extremely radioactive and unstable; generally, the heavier isotopes are more stable than the lighter ones. The most stable and well-known roentgenium isotope is 282Rg, which is also the heaviest known roentgenium isotope; it has a half-life of 100 seconds. The unconfirmed 286Rg is heavier and appears to contain a longer half-life of around 10.7 minutes, which would make it the longest-lived superheavy known nuclides. In the same manner, the unconfirmed 283Rg appears to hold a long half-life of 5.1 minutes. The isotopes 281Rg, 280Rg have also been reported to hold half-lives over a second. Moreover, the remaining isotopes contain half-lives in the range of a millisecond.

Uses of Roentgenium

Roentgenium is described as a synthetic, radioactive element where a little is known. It is expected to be solid at room temperature and classified as a metal.

Roentgenium contains 7 isotopes whose half-lives are entirely known. One of the most stable isotopes is the 281 Rg, having a half-life of around 26 seconds. It decays via spontaneous fission.

Sources of Roentgenium

Roentgenium can be produced artificially. The team that participated in its discovery bombarded the bismuth atoms with nickel ions in a linear accelerator to produce the 111 elements.

Uses of Roentgenium

Only a few roentgenium atoms have ever been made, and they contain no current application beyond the scientific study.

FAQ (Frequently Asked Questions)

Q1. How Did the Discovery of Roentgenium Happen?

Answer: Rogentium element was not discovered because it does not exist in the crust of the earth. Instead, it was synthesized in 1994 by an international team located in Germany by bismuth bombardment with nickel. They also yielded a single atom of rogentium-272.

Q2. Why are Transition Elements Called So?

Answer: The transition metals are called so because one of the English chemists, named Charles Bury, described them as the bunch of elements that fill the inner shells (d-block fills the n-1 shell) and "bridge" the stable transition states. For example, in the 3rd period, the stable states contain 8 electrons, whereas there are also stable states with 18 electrons, where those 10 electrons are in the d-shell.

Q3. What are the Transition Elements?

Answer: Transition elements are the d -block elements in the periodic table. They are called so because their valencies represent the transitions. It means it varies. Also, these variable valencies of the transition elements are because of the presence of empty d-orbitals.

Q4. Which One is the Least Dense Element?

Answer: Under the standard conditions, lithium is considered the lightest metal and the least dense solid element. It is a silver-white and soft metal that belongs to the alkali metal group of chemical elements.