Seaborgium – facts and properties
- Symbol
- Sg
- Atomic number
- 106
- Atomic mass
- 269 u
- Period
- 7
- Group
- 6
- Category
- transition metal
- Electron configuration
- [Rn] 5f¹⁴ 6d⁴ 7s²
- Valence electrons
- 6
- State at standard conditions
- solid
- Discovered
- 1974
Seaborgium is a radioactive laboratory element with atomic number 106. It is named after the American nuclear chemist Glenn T. Seaborg, and it was the first element whose name was officially confirmed while the person honoured was still alive. Chemically it belongs to group 6, below tungsten. It is made one atom at a time in accelerators. Nearly all its properties are predicted, though a few experiments back up the kinship with tungsten.
Position in the periodic table
Occurrence and extraction
Seaborgium has no natural occurrence. All its isotopes are radioactive. The longest half-lives reported in the literature are a few minutes, but the values are uncertain because only a few atoms have been observed. Other isotopes halve within seconds or fractions of one.
A group at Berkeley made the element in 1974 by bombarding a californium target with oxygen ions. In the same year the group around Yuri Oganessian at Dubna reported signs of its own, using lead bombarded with chromium ions. The international working group that later weighed the claims recognised Berkeley as the discoverer.
The name is unusual. Glenn Seaborg lived from 1912 to 1999. In 1951 he shared the Nobel Prize in Chemistry with Edwin McMillan, he took part in discovering several transuranium elements, and in 1944 he proposed placing the heavy elements in a series of their own beneath the lanthanoids. That actinoid series now appears in every periodic table. Berkeley proposed the name seaborgium only in 1994, after its discovery had been recognised. An IUPAC committee at first refused it, because the rule was not to name elements after living people, but protest from American chemists reversed this, and the name became official in 1997. Seaborg lived to see it. That makes seaborgium the first element whose name was officially confirmed in its honouree's lifetime. The names einsteinium and fermium had been proposed while Einstein and Fermi were alive, but were announced only in 1955, after both had died. So far the only second case is oganesson.
Properties and reactions
Seaborgium is in period 7 and group 6, below tungsten, with molybdenum and chromium higher up. The electron configuration [Rn] 5f¹⁴ 6d⁴ 7s² has only been calculated. The atomic mass is given as 269 u, the mass number of seaborgium-269, one of the longer-lived isotopes. No sample of the metal has ever existed. Density, melting point and boiling point are unmeasured.
From its position, seaborgium is expected to show the oxidation state plus six most often, with oxo compounds and oxide chlorides like molybdenum and tungsten. In experiments of the 1990s on a few atoms, in the gas phase and in solution, it did behave that way. These are observations on a handful of atoms, not precise measurements.
The most striking experiment came in 2014. An international team led by groups from Mainz and Darmstadt, working at the Japanese research centre RIKEN produced seaborgium atoms, slowed them in a mixture of helium and carbon monoxide, and detected a volatile compound that is interpreted as seaborgium hexacarbonyl, Sg(CO)₆. It corresponds to the hexacarbonyls of chromium, molybdenum and tungsten. It was the first time a bond between a superheavy element and carbon had been shown. The formula was assigned by comparing with calculations, not by determining the structure directly.
Research and synthesis
Seaborgium finds no use outside the laboratory. It is used to test how far the group rules of the periodic table carry.
It is made in fusion reactions, for instance curium with neon ions. The atoms form in a thin target, a separator divides them from the beam particles, and a detector records their decays. In 2014, two weeks of round-the-clock running yielded only 18 detected atoms. Volatile complexes such as the hexacarbonyl suit this kind of study well, since they are easy to separate in the gas phase.
The element itself poses no danger, because it exists only as single atoms. Radiation protection concerns the accelerators and the radioactive targets.
Quick question
What is the atomic number of seaborgium (Sg)?
FAQ
Was seaborgium the first element named after a living person?
Its name was officially confirmed in 1997, while Glenn Seaborg was alive. He died in 1999. In that sense it was the first such case, and oganesson is the second.
How similar is seaborgium to tungsten?
Quite similar, judging by the experiments so far. Like molybdenum and tungsten it forms compounds in the oxidation state plus six, and a volatile hexacarbonyl. All of this rests on a few atoms.
What is seaborgium used for?
It is studied only in basic research. It lets scientists check whether the periodic table and the calculation methods for heavy atoms hold up for the largest known nuclei.