Isotopes of Hydrogen
Category : JEE Main & Advanced
Isotopes are the different forms of the same element, which have the same atomic number but different mass numbers.
Isotopes of hydrogen
| Name | Symbol | Atomic number | Mass number | Relative abundance | Nature radioactive or non-radioactive |
| Protium or Hydrogen | \[_{1}^{1}\text{H}\]or H | 1 | 1 | 99.985% | Non-radioactive |
| Deuterium | \[_{\text{1}}^{\text{2}}\text{H}\]or D | 1 | 2 | 0.015% | Non-radioactive |
| Tritium | \[_{\text{1}}^{\text{3}}\text{H}\]or T | 1 | 3 | \[{{10}^{-15}}\]% | Radioactive |
Physical constants of H2 , D2 and T2
| Property | H2 | D2 | T2 |
| Molecular mass | 2.016 | 4.028 | 6.03 |
| Melting point (K) | 13.8 | 18.7 | 20.63 |
| Boiling point (K) | 20.4 | 23.9 | 25.0 |
| Heat of fusion \[\text{(kJ}\,\text{mo}{{\text{l}}^{\text{-1}}})\] | 0.117 | 0.197 | 0.250 |
| Heat of vaporisation \[\text{(kJ}\,\text{mo}{{\text{l}}^{\text{-1}}})\] | 0.994 | 1.126 | 1.393 |
| Bond energy \[\text{(kJ}\,\text{mo}{{\text{l}}^{\text{-1}}})\] | 435.9 | 443.4 | 446.9 |
Isotopic effect : In general chemical properties of isotopes are same but quantiative differences are noticed amongst them. For example, the reaction between \[{{H}_{2}}\] and \[C{{l}_{2}}\] is 13.4 times faster between \[{{D}_{2}}\] and \[C{{l}_{2}}\] under similar conditions. Such differences in chemical properties, which are due to difference in the mass numbers of isotopes is known as isotopic effect.
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