同位素的化学性质一般很相象，但是，对重水里面的重氢来说这是错误的，因为它具有最小的原子量，所以核子数量的变动对重氢原子的化学性质是有影响的，而生物系统对氢键的强度是非常敏感的（如DNA双链的强度）。一个人如果只摄入重水的话是必死无疑的，但不是因为脱水而是由于生理机能紊乱。
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Heavy isotopes of chemical elements have very slightly different chemical behaviors, but for most elements the differences in chemical behavior between isotopes are far too small to use, or even detect. For hydrogen, however, this is not true. The larger chemical isotope-effects seen with deuterium and tritium manifest because bond energies in chemistry are determined in quantum mechanics by equations in which the quantity of reduced mass of the nucleus and electrons appears. This quantity is altered in heavy-hydrogen compounds (of which deuterium oxide is the most common and familiar) far more greatly than for heavy-isotope substitution in other chemical elements. This isotope effect of heavy hydrogen is magnified further in biological systems, which are very sensitive to small changes in the solvent properties of water. |
