Hassium

group 8 · period 7 · d-block · transition metal

Identity

Name and symbol: Hassium, Hs
Atomic number: 108 protons
Position: group 8 · period 7 · d-block · transition metal
CAS number: 54037-57-9

Atomic structure

Atomic mass: 270 u
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d⁶
[Rn] 7s²⁵f¹⁴⁶d⁶
Electrons per shell: 2, 8, 18, 32, 32, 14, 2
Valence electrons: 8 ns and (n-1)d

nuclide	half-life	decay
²⁷⁷Hsm	130 s	SF=100%
²⁶⁹Hs	15 s	α=100%
²⁷¹Hs	10 s [Estimated]	α ?; SF ?
²⁷²Hs	10 s [Estimated]	α ?; SF ?

no stable isotope; the longest-lived nuclides

Physical properties

State at room temperature: Solid
Melting point: not in sources
Boiling point: not in sources
Density: not in sources
Appearance: not in sources
Thermal conductivity: not in sources
Electrical resistivity: not in sources
Electrical conductivity: not in sources
Crystal structure: hexagonal close-packed
Molar heat capacity: not in sources

Chemical properties

Oxidation states: 8, (6), (5), (4), (3), (2)(parenthesized oxidation states are predictions)
Electronegativity: not in sources
Ionisation energy: 7.6 eV
Electron affinity: not in sources
Atomic radius: not in sources
Ionic radius: not in sources

Reactivity: A group 8 transactinide; seven atoms oxidized in 2001 gave a volatile tetroxide HsO4 like osmium tetroxide, and in 2004 that tetroxide underwent the first acid-base reaction of a hassium compound, placing hassium firmly under osmium in the +8 state.
with water: Not known for the element; the tetroxide reacts with aqueous sodium hydroxide: $\ce{HsO4 + 2 NaOH -> Na2HsO4(OH)2}$ .
with oxygen, air: Single atoms in a helium and oxygen stream form the tetroxide: $\ce{Hs + 2 O2 -> HsO4}$ , slightly less volatile than OsO4.
with acids: Not known; no experiment with acids has been reported.
with halogens: Not known; no experiment has been reported.

Typical compounds

HsO₄ hassium tetroxide volatile, detected on seven atoms in 2001
Na₂HsO₄(OH)₂ sodium hassate(VIII) from HsO4 and sodium hydroxide, 2004

Occurrence, production and use

Crustal abundance: Not Applicable
Oceanic abundance: Not Applicable

Occurrence and sources

synthetic only lead bombarded with iron atoms

Extraction, production: not in sources

Uses: Since only small amounts of hassium have ever been produced, it currently has no uses outside of basic scientific research.

Safety, toxicity: not in sources

Discovery and name

Discovered by: Gesellschaft für Schwerionenforschung
Discovered: 1984
First isolated: not in sources
Named by: not in sources
Origin of the name: after Hassia, Latin for Hesse, Germany, where it was discovered

Hassium does not occur naturally in the Earth’s crust. Hassium was first synthesized by German scientists at the GSI Center for Heavy Ion Research in Darmstadt, Germany in 1984 using the nuclear reaction 208Pb (58Fe, n) 265Hs (Fig. IUPAC.108.1). The element is named for Hassia (the Latin name for the German state of Hesse), whose former capital was Darmstadt [651], [652], [653]. Hassium is used in chemical and heavy element research.

Conventions

Valence electrons are counted by the usual convention: the outer shell for s- and p-block elements, ns and (n-1)d for the d-block, ns, (n-1)d and (n-2)f for the f-block. Lanthanides and actinides are placed in the f-block with no group number. Electrical conductivity is the reciprocal of the printed resistivity. Ionic radii are Shannon effective radii, six-coordinate unless noted. Where a field reads “not in sources” the value was not found; it is a gap, not a zero. Regulatory limits are the published values and change often, so check the standard in force at your site and the numbers written into your own permit before you design to them.

Data

Element records, isotopes, radii and the descriptive text come from PubChem (NCBI), the Los Alamos National Laboratory periodic table, IUPAC CIAAW and the IAEA Atomic Mass Data Center. Appearance, thermal conductivity, electrical resistivity, crystal structure, discovery and the origin of each name come from Wikipedia and Periodic-Table-JSON, used under CC BY-SA 4.0. Hazard classifications come from the ECHA C&L inventory via PubChem. Ionic radii follow R. D. Shannon (1976). The water chapters cite their own sources at the foot of each entry, and are written to the level of Snoeyink and Jenkins, Stumm and Morgan, MWH's Water Treatment and Metcalf and Eddy.