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Iron-60 is an iron isotope with a half-life of 2.6 million years, [12] [13] but was thought until 2009 to have a half-life of 1.5 million years. It undergoes beta decay to cobalt-60 , which then decays with a half-life of about 5 years to stable nickel-60.
An even number of protons or neutrons is more stable (higher binding energy) because of pairing effects, so even–even nuclides are much more stable than odd–odd. One effect is that there are few stable odd–odd nuclides: in fact only five are stable, with another four having half-lives longer than a billion years.
Iron(II) complexes are less stable than iron(III) complexes but the preference for O-donor ligands is less marked, so that for example [Fe(NH 3) 6] 2+ is known while [Fe(NH 3) 6] 3+ is not. They have a tendency to be oxidized to iron(III) but this can be moderated by low pH and the specific ligands used. [72]
Iron(II) complexes are less stable than iron(III) complexes but the preference for O-donor ligands is less marked, so that for example [Fe(NH 3) 6] 2+ is known while [Fe(NH 3) 6] 3+ is not. They have a tendency to be oxidized to iron(III) but this can be moderated by low pH and the specific ligands used. [18]
Below 912 °C (1,674 °F), iron has a body-centered cubic (bcc) crystal structure and is known as α-iron or ferrite.It is thermodynamically stable and a fairly soft metal. α-Fe can be subjected to pressures up to ca. 15 GPa before transforming into a high-pressure form termed ε-Fe discussed below.
For example, the complex [Ni(dien) 2)] 2+ is more stable than the complex [Ni(en) 3)] 2+; both complexes are octahedral with six nitrogen atoms around the nickel ion, but dien (diethylenetriamine, 1,4,7-triazaheptane) is a tridentate ligand and en is bidentate. The number of chelate rings is one less than the number of donor atoms in the ligand.
Hexaferrum and epsilon iron (ε-Fe) are synonyms for the hexagonal close-packed (HCP) phase of iron that is stable only at extremely high pressure.. A 1964 study at the University of Rochester mixed 99.8% pure α-iron powder with sodium chloride, and pressed a 0.5-mm diameter pellet between the flat faces of two diamond anvils.
The rarer isotopes nickel-62 and iron-58, which both have higher binding energies, are not shown. Iron-56 (56 Fe) is the most common isotope of iron. About 91.754% of all iron is iron-56. Of all nuclides, iron-56 has the lowest mass per nucleon. With 8.8 MeV binding energy per nucleon, iron-56 is one of the most tightly bound nuclei. [1]