Atomic and nuclear properties of materials:
Roentgenium (Rg)

Quantity	Value	Units
Atomic number	111
Atomic mass	[280.164(5)]	g mole-1
Density	??	g cm-3
Mean excitation energy	1143.0	eV
Minimum ionization	1.091	MeV g-1cm2
Nuclear collision length	124.2	g cm-2
Nuclear interaction length	220.7	g cm-2
Pion collision length	146.8	g cm-2
Pion interaction length	246.5	g cm-2
Radiation length	5.14	g cm-2
Critical energy	5.88	MeV (for e-)
Molière radius	18.56	g cm-2
Plasma energy	67.87	eV
Muon critical energy	111.	GeV

For muons, dE/dx = a(E) + b(E) E. Tables of b(E): PS PDF TEXT
Table of muon dE/dx and Range: PS PDF TEXT
Explanation of some entries
Note: Since there is no stable isotope, [atomic mass] is that of the longest-lived known isotope as of Jan 2007.
Note: Density 14.0 g/cm³ and I_eff = 1143 eV assumed in calculating critical energies and dE/dx.
Table of isotopes Warning: may not be current