Unbinilium
Unbinilium, also known as eka-radium or element 120, is a hypothetical chemical element; it has symbol Ubn and atomic number 120. Unbinilium and Ubn are the temporary systematic IUPAC name and symbol, which are used until the element is discovered, confirmed, and a permanent name is decided upon. In the periodic table of the elements, it is expected to be an s-block element, an alkaline earth metal, and the second element in the eighth period. It has attracted attention because of some predictions that it may be in the island of stability.
| Theoretical element | ||||||
|---|---|---|---|---|---|---|
| Unbinilium | ||||||
| Pronunciation | /ˌuːnbaɪˈnɪliəm/ | |||||
| Alternative names | element 120, eka-radium | |||||
| Unbinilium in the periodic table | ||||||
| ||||||
| Atomic number (Z) | 120 | |||||
| Group | group 2 (alkaline earth metals) | |||||
| Period | period 8 (theoretical, extended table) | |||||
| Block | s-block | |||||
| Electron configuration | [Og] 8s2 (predicted) | |||||
| Electrons per shell | 2, 8, 18, 32, 32, 18, 8, 2 (predicted) | |||||
| Physical properties | ||||||
| Phase at STP | solid (predicted) | |||||
| Melting point | 953 K (680 °C, 1256 °F) (predicted) | |||||
| Boiling point | 1973 K (1700 °C, 3092 °F) (predicted) | |||||
| Density (near r.t.) | 7 g/cm3 (predicted) | |||||
| Heat of fusion | 8.03–8.58 kJ/mol (extrapolated) | |||||
| Atomic properties | ||||||
| Oxidation states | (+1), (+2), (+4), (+6) (predicted) | |||||
| Electronegativity | Pauling scale: 0.91 (predicted) | |||||
| Ionization energies |
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| Atomic radius | empirical: 200 pm (predicted) | |||||
| Covalent radius | 206–210 pm (extrapolated) | |||||
| Other properties | ||||||
| Crystal structure | body-centered cubic (bcc) (extrapolated) | |||||
| CAS Number | 54143-58-7 | |||||
| History | ||||||
| Naming | IUPAC systematic element name | |||||
| Isotopes of unbinilium | ||||||
| Experiments and theoretical calculations | ||||||
Unbinilium has not yet been synthesized, despite multiple attempts from German and Russian teams. Experimental evidence from these attempts shows that the period 8 elements would likely be far more difficult to synthesise than the previous known elements. New attempts by American and Russian teams to synthesize unbinilium are planned to begin in the mid-2020s.
Unbinilium's position as the seventh alkaline earth metal suggests that it would have similar properties to its lighter congeners; however, relativistic effects may cause some of its properties to differ from those expected from a straight application of periodic trends. For example, unbinilium is expected to be less reactive than barium and radium and be closer in behavior to strontium, and while it should show the characteristic +2 oxidation state of the alkaline earth metals, it is also predicted to show the +4 and +6 oxidation states, which are unknown in any other alkaline earth metal.