Atomic and nuclear properties of materials:
Neutron (n)

Quantity	Value	Units	Value	Units
Atomic number	0	n	n	n
Mass	+/- 1.008 664 915 97 +/- 0.000 000 000 43	u	+/- 939.565 346 +/- 000.000 023	MeV
Nuclear density	mmmfew x 1015	g cm-3	n	n

Mass values from physics.nist.gov/cuu/Constants (2006)