Editing Nobelium (section)

==Preparation and purification==
The isotopes of nobelium are mostly produced by bombarding actinide targets ([[uranium]], [[plutonium]], [[curium]], [[californium]], or [[einsteinium]]), with the exception of nobelium-262, which is produced as the [[decay product|daughter]] of lawrencium-262.<ref name="Silva16378" /> The most commonly used isotope, <sup>255</sup>No, can be produced from bombarding [[curium]]-248 or californium-249 with carbon-12: the latter method is more common. Irradiating a 350&nbsp;[[microgram|μg]]&nbsp;cm<sup>−2</sup> target of californium-249 with three&nbsp;trillion (3&nbsp;×&nbsp;10<sup>12</sup>) 73&nbsp;[[electronvolt|MeV]] carbon-12 ions per second for ten minutes can produce around 1200 nobelium-255 atoms.<ref name="Silva16378" />

Once the nobelium-255 is produced, it can be separated out similarly as used to purify the neighboring actinide mendelevium. The recoil [[momentum]] of the produced nobelium-255 atoms is used to bring them physically far away from the target from which they are produced, bringing them onto a thin foil of metal (usually [[beryllium]], [[aluminium]], [[platinum]], or [[gold]]) just behind the target in a vacuum: this is usually combined by trapping the nobelium atoms in a gas atmosphere (frequently [[helium]]), and carrying them along with a gas jet from a small opening in the reaction chamber. Using a long [[capillary tube]], and including [[potassium chloride]] aerosols in the helium gas, the nobelium atoms can be transported over tens of [[meter]]s.<ref name="Silva16389">{{harvnb|Silva|2011|pp=1638–9}}</ref> The thin layer of nobelium collected on the foil can then be removed with dilute acid without completely dissolving the foil.<ref name="Silva16389" /> The nobelium can then be isolated by exploiting its tendency to form the divalent state, unlike the other trivalent actinides: under typically used [[elution]] conditions ([[bis-(2-ethylhexyl) phosphoric acid]] (HDEHP) as stationary organic phase and 0.05&nbsp;M&nbsp;[[hydrochloric acid]] as mobile aqueous phase, or using 3&nbsp;M&nbsp;hydrochloric acid as an eluant from [[cation-exchange]] resin columns), nobelium will pass through the column and elute while the other trivalent actinides remain on the column.<ref name="Silva16389" /> However, if a direct "catcher" gold foil is used, the process is complicated by the need to separate out the gold using [[anion-exchange]] [[chromatography]] before isolating the nobelium by elution from [[chromatography|chromatographic]] extraction columns using HDEHP.<ref name="Silva16389" />