Formula:  or 
* Density: 0.180 kg/m at STP (0 °C, 101325 Pa).
* Atomic weight: 2.0141017926 Da.
* Mean abundance in ocean water (from VSMOW) 155.76 ± 0.1 atoms of deuterium per million atoms of all isotopes of hydrogen (about 1 atom of in 6420); that is, about 0.015% of all atoms of hydrogen (any isotope)
Data at approximately 18 K for H (triple point):
* Density:
** Liquid: 162.4 kg/m
** Gas: 0.452 kg/m
* Viscosity: 12.6 μPa·s at 300 K (gas phase)
* Specific heat capacity at constant pressure c:
** Solid: 2950 J/(kg·K)
** Gas: 5200 J/(kg·K)