10.3A: Protium and Deuterium
- Page ID
- 34052
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Properties of hydrogen
The difference of mass between isotopes of most elements is only a small fraction of the total mass and so this has very little effect on their properties, this is not the case for hydrogen. Consider chlorine with Z=17, there are 2 stable isotopes 35Cl (75.77%) and 37Cl (24.23%). The increase is therefore 2 in 35 or less than 6%. Deuterium and tritium are about double and triple the mass of protium and show significant physical and chemical differences particularly with regard to those properties related to mass, e.g. rate of diffusion, density, etc.
| isotope | MP /K | BP /K | ΔHdiss /kJmol-1 | Interatomic Distance /pm |
|---|---|---|---|---|
| H2 | 13.99 | 20.27 | 435.99 | 74.14 |
| D2 | 18.73 | 23.67 | 443.4 | 74.14 |
| T2 | 20.62 | 25.04 | 446.9 | 74.14 |
| Property | H2O | D2O |
|---|---|---|
| Melting point /K | 273.15 | 276.97 |
| Boiling point /K | 373.15 | 374.5 |
| Temperature of maximum density /K | 277 | 284.2 |
| Maximum density /g cm3 | 0.99995 | 1.1053 |
| Relative permittivity (at 298 K) | 78.39 | 78.06 |
| Kw (at 298 K) | 1 *1014 | 2 * 1015 |
| Symmetric stretch, ν1 /cm-1 (gaseous molecule) |
3657 | 2671 |