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The abundance of the Group 13 elements is given in [link] . Aluminum is the most abundant metal in the Earth’s crust and is found in a wide range of minerals. While boron is not as common it is also found in a range of borate minerals. In contrast, gallium, indium, and thallium are found as impurities in other minerals. In particular indium and thallium are found in sulfide or selenide mineral rather than oxides, while gallium is found in both sulfides (ZnS) and oxides (bauxite). Although indium and thallium minerals are known, they are rare: indite (FeIn 2 S 4 ), lorandite (TlAsS 2 ), crookesite (Cu 7 TlSe 4 ).
| Element | Terrestrial abundance (ppm) |
| B | 10 (Earth’s crust), 20 (soil), 4 (sea water) |
| Al | 82,000 (Earth’s crust), 100,000 (soil), 5 x 10 -4 (sea water) |
| Ga | 18 (Earth’s crust), 28 (soil), 30 x 10 -6 (sea water) |
| In | 0.1 (Earth’s crust), 0.01 (soil), 0.1 x 10 -6 (sea water) |
| Tl | 0.6 (Earth’s crust), 0.2 (soil), 10 x 10 -6 (sea water) |
The naturally abundant isotopes of the Group 13 elements are listed in [link] . Thallium has 25 isotopes that have atomic masses that range from 184 to 210. Thallium-204 is the most stable radioisotope, with a half-life of 3.78 years.
| Isotope | Natural abundance (%) |
| Boron-10 | 19.9 |
| Boron-11 | 80.1 |
| Aluminum-27 | 100 |
| Gallium-69 | 60.11 |
| Gallium-71 | 39.89 |
| Indium-113 | 4.3 |
| Indium-115 | 95.7 |
| Thallium-203 | 29.52 |
| Thallium-205 | 70.48 |
The Group 13 elements offer potential as NMR nuclei ( [link] ). In particular 11 B and 27 Al show promise for characterization in both solution and solid state.
| Isotope | Spin | Natural abundance (%) | Quadrupole moment (10 -30 m 2 ) | NMR frequency (MHz) at a field of 2.3488 T | Reference |
| Boron-10 | 3 | 19.58 | 8.459 | -10.746 | BF 3 .Et 2 O |
| Boron-11 | 3 / 2 | 80.42 | 4.059 | -32.084 | BF 3 .Et 2 O |
| Aluminum-27 | 5 / 2 | 100 | 14.66 | -26.057 | Al(NO 3 ) 3 |
| Gallium-69 | 3 / 2 | 60.4 | 17.1 | -24.003 | Ga(NO 3 ) 3 |
| Gallium-71 | 3 / 2 | 39.6 | 10.7 | -30.495 | Ga(NO 3 ) 3 |
| Indium-113 | 9 / 2 | 4.28 | 79.9 | -21.866 | In(NO 3 ) 3 |
| Indium-115 | 9 / 2 | 95.72 | 81.0 | -21.914 | In(NO 3 ) 3 |
Borax is mined as a mixture of Na 2 B 4 O 7 .4H 2 O and Na 2 B 4 O 7 .10H 2 O. Acidification gives boric acid, B(OH) 3 , which can be reduced with sodium amalgam (Na/Hg) to give amorphous boron. Pure boron can be prepared by reducing boron halides (e.g., BF 3 and BCl 3 ) with hydrogen at high temperatures. Ultrapure boron, for the use in semiconductor industry, is produced by the decomposition of diborane (B 2 H 6 ) and then further purified with the zone melting or Czochralski processes.
The only two economic sources for gallium are as byproduct of aluminum and zinc production. Extraction during the Bayer process followed by mercury cell electrolysis and hydrolysis of the amalgam with sodium hydroxide leads to sodium gallate. Electrolysis then gives gallium metal.
The lack of indium mineral deposits and the fact that indium is enriched in sulfides of lead, tin, copper, iron and zinc, makes the zinc production the main source for indium. The indium is leached from slag and dust of zinc production. Up until 1924, there was only about a gram of isolated indium on the planet, however, today worldwide production is currently greater 476 tons per year from mining and a 650 tons per year from recycling. This massive increase in demand is due to applications in LCD displays and solar cell applications.
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