Expected headings
"Basic chemistry"
"Nutrition"
"There are four stable isotopes of iron, of which iron-56, the commonest on earth accounts for 91.7%, whilst iron-54, the second commonest isotope comprises a further 5.8%. Iron-57 comprises most of the rest of global iron (2.1 %) and iron-58 only a tiny percentage (0.2%) 4. A further 27 unstable isotopes are known, with the one showing most promise in nuclear medicine being iron-52 (half-life 8.3 hours), which is a positron emitter and is used for PET 4,5."