Atomic and nuclear properties of materials:
Francium (Fr)

Quantity	Value	Units	Value	Units
Atomic number	87
Atomic mass	[223.01974(2)]	g mole-1
Density	1.87	g cm-3
Mean excitation energy	827.0	eV
Minimum ionization	1.118	MeV g-1cm2	2.091	MeV cm-1
Nuclear collision length	116.4	g cm-2	62.27	cm
Nuclear interaction length	204.6	g cm-2	109.4	cm
Pion collision length	139.5	g cm-2	74.62	cm
Pion interaction length	230.9	g cm-2	123.5	cm
Radiation length	6.19	g cm-2	3.309	cm
Critical energy	7.59	MeV (for e-)	7.32	MeV (for e+)
Molière radius	17.29	g cm-2	9.247	cm
Plasma energy	24.61	eV
Muon critical energy	143.	GeV
Melting point	300.1	K	27.00	C
Boiling point @ 1 atm	950.2	K	677.0	C

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: Francium is less stable than any other element lighter than nobelium, element 102.
Note: Since there is no stable isotope, [atomic mass] is that of the longest-lived known isotope as of Jan 2007.
Table of isotopes Warning: may not be current
x ray mass attenuation coefficients