Roentgenium (pronounced /rɛntˈɡɛniəm/ or /rʌntˈɡɛniəm/ ( listen)) is a synthetic radioactive chemical element with the symbol Rg and atomic number 111. It is placed as the heaviest member of the group 11 (IB) elements, although a sufficiently stable isotope is not known at this time that would allow its position as a heavier homologue of gold to be confirmed.
Roentgenium was first observed in 1994 and several isotopes have been synthesized since...
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Roentgenium
Chemical Element
The 111th Element in the Periodic Table
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Darmstadtium
Darmstadtium (pronounced /dɑrmˈʃtætiəm/ ( listen)) darm-SHTAT-ee-əm, formerly known as ununnilium, is a chemical element with the symbol Ds and...
Symbol:
- Rg
Atomic mass:
- 272 u (4.52E-16 µg )
Isotopes:
- Roentgenium-278
- Roentgenium-277
- Roentgenium-272
- Roentgenium-283
- Roentgenium-280
- Roentgenium-279
- Roentgenium-276
- Roentgenium-273
- Roentgenium-275
- Roentgenium-281
Chemical series:
Periodic table block:
Discovery Date:
- 1994