This stable monoisotopic element belongs to block p, to group 13 and to period 5 and to group IIIA called boron of the periodic table as well as to the family of poor metals. The atomic radius of indium is around 150 pm (1.50 Å).

The simple indium In body is a shiny gray metal, with a low melting point barely above 156 ¡ă C, resistant to atmospheric corrosion.

This malleable metal has a chemistry quite similar to aluminum and gallium, but also to cadmium and thallium. The electronegativity according to Pauling is of the order of 1.7 (̠8), while those of Ga and Al are around 1.6 and 1.5 respectively.

It is rare. Indium remained a ¡°metal or laboratory element¡± until the beginning of the interwar period10. In 1924, we discovered that indium can stabilize non-ferrous metals11. In 1940, indium as a long-lasting protective and anti-corrosion coating improved ball bearings in military aeronautical equipment. In the early 1970s, according to chemist Bruce Mahan (en), indium did not show any significant use. In the early 1980s, the chemical contributors to the Encyclopedia Universalis admitted that there are few indium compounds studied and well known (probably for applications). Its recent massive use, particularly in LCD flat screens, has increased its price from 80 to 800 € / kg (70 to 1 000 $ / kg at current rates12) between 2001 and 200513,14. The current shortage makes it a critical mineral raw material.

Indium has 39 known isotopes, with a mass number varying between 97 and 135, and 47 nuclear isomers. Among these isotopes, only one is stable, 113In, making indium a monoisotopic element. However, natural indium also consists and even predominantly (~ 95.7%) of a weakly radioactive radioisotope, 115In, with a half-life of around 441,000 billion years, which means that indium is not a mononucleidic element. Indium also shares the characteristic with rhenium and tellurium of having a long-lived natural radioisotope more abundant than its stable isotope (s). The standard atomic mass attributed to indium is 114.818 (3) u



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