Atomic and nuclear properties of materials:
Polonium (Po)

Quantity	Value	Units	Value	Units
Atomic number	84
Atomic mass	[209.9829]	g mole-1
Specific gravity	9.32	g cm-3
Minimum ionization	1.135	MeV g-1cm2	10.58	MeV cm-1
Nuclear collision length	114.5	g cm-2	12.29	cm
Nuclear interaction length	200.5	g cm-2	21.52	cm
Radiation length	6.19	g cm-2	0.6643	cm
Critical energy	7.33	MeV (for e-)	7.06	MeV (for e+)
Molière radius	17.91	g cm-2	1.922	cm
Plasma energy	55.64	eV
Muon critical energy	139.	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, given atomic mass is that of the longest-lived known isotope as of Jan 2007.
Table of isotopes
x ray mass attenuation coefficients