Chemistry · Ch 8 — Elements of Group 1 and 2
Isotopes of Hydrogen
Isotopes of Hydrogen
Isotopes are atoms of the same element — meaning they share the same number of protons, and so the same atomic number — that differ from one another in mass number because they carry different numbers of neutrons. Hydrogen has three isotopes, all with one proton and one electron but differing neutron counts: protium (¹H, no neutron, by far the most abundant, essentially the 'ordinary' hydrogen), deuterium (²H or D, one neutron) and tritium (³H or T, two neutrons). Protium and deuterium are both stable; tritium, present only in trace amounts in nature, is radioactive — its nucleus is unstable and decays …
What this figure shows. A schematic nucleus-and-electron diagram comparing the three isotopes of hydrogen side by side, each drawn as a small central nucleus (made of the labelled p = proton and n = neutron particles) with its mass number and atomic number written as superscript/subscript on the symbol H. Protium () is shown with a nucleus of just one proton and no neutron. Deuterium () is shown with a nucleus of one proton plus one neutron. Tritium () is shown with a nucleus of one proton plus two neutrons. All three are drawn with a single electron around the nucleus, since all isotopes of an element h …
Table 8.1 — Characteristics of the isotopes of hydrogen (name | symbol | atomic number Z | atomic mass number A | neutron number N | abundance | stability):
Hydrogen (Protium), symbol H or ¹H (also written H-1): Z = 1, A = 1, N = 0, abundance ≈ 99.98%, stable.
Deuterium, symbol D or ²H (also written H-2): Z = 1, A = 2, N = 1, abundance ≈ 0.015%, stable.
Tritium, symbol T or ³H (also written H-3): Z = 1, A = 3, N = 2, abundance only a trace, radioactive. …