Atomic and nuclear properties of roentgenium (Rg)
Atomic number 111  
Atomic mass [282.1691(7)] g mole-1
Specific gravity ?? g cm-3
Mean excitation energy 1143.0 eV
Minimum ionization 1.091 MeV g-1cm2
Nuclear collision length 124.5 g cm-2
Nuclear interaction length 221.2 g cm-2
Pion collision length 147.1 g cm-2
Pion interaction length 247.1 g cm-2
Radiation length 5.18 g cm-2
Critical energy 5.93 MeV (for e-)
Molière radius 18.54 g cm-2
Plasma energy ωp 67.87 eV
Muon critical energy 111. GeV
For muons, dE/dx = a(E) + b(E) E. Tables of b(E): PDF TEXT
Table of muon dE/dx and Range: PDF TEXT
Explanation of some entries
Note: Since there are no stable isotopes, [atomic mass] is that of the longest-lived isotope known as of Jun 2017.
Note: Density 14.0 g/cm3 and Ieff = 1143 eV assumed in calculating critical energies and dE/dx.
Table of isotopes via WIKIPEDIA