Editing Berkelium (section)

===Physical===
[[File:Closest packing ABAC.png|thumb|Double-hexagonal close packing with the layer sequence ABAC in the crystal structure of α-berkelium (A: green, B: blue, C: red)|alt=Sequential layers of spheres arranged from top to bottom: GRGBGRGB (G=green, R=red, B=blue)]]

Berkelium is a soft, silvery-white, radioactive [[actinide]] metal. In the [[periodic table]], it is located to the right of the actinide [[curium]], to the left of the actinide [[californium]] and below the lanthanide [[terbium]] with which it shares many similarities in physical and chemical properties. Its density of 14.78&nbsp;g/cm<sup>3</sup> lies between those of curium (13.52&nbsp;g/cm<sup>3</sup>) and californium (15.1&nbsp;g/cm<sup>3</sup>), as does its melting point of 986&nbsp;°C, below that of curium (1340&nbsp;°C) but higher than that of californium (900&nbsp;°C).<ref name="CRC" /> Berkelium is relatively soft and has one of the lowest [[bulk modulus|bulk moduli]] among the actinides, at about 20 [[Pascal (unit)|GPa]] (2{{e|10}}&nbsp;Pa).<ref name="pressure" />

{{Not a typo|Berkelium(III)}} ions shows two sharp [[fluorescence]] peaks at 652&nbsp;[[nanometre|nanometer]]s (red light) and 742&nbsp;nanometers (deep red – [[Infrared#Regions within the infrared|near-infrared]]) due to internal transitions at the [[Electron configuration|f-electron shell]]. The relative intensity of these peaks depends on the excitation power and temperature of the sample. This emission can be observed, for example, after dispersing berkelium ions in a silicate glass, by melting the glass in presence of berkelium oxide or halide.<ref>{{cite journal|last1=Assefa|first1=Z.|last2=Haire|first2=R. G.|last3=Stump|first3=N. A.|title=Emission profile of Bk(III) in a silicate matrix: anomalous dependence on excitation power|journal=Journal of Alloys and Compounds|volume=271-273|pages=854–858|date=1998|doi=10.1016/S0925-8388(98)00233-3|url=https://zenodo.org/record/1260149}}</ref><ref>Rita Cornelis, Joe Caruso, Helen Crews, Klaus Heumann [https://books.google.com/books?id=1PmjurlE6KkC&pg=PA553 Handbook of elemental speciation II: species in the environment, food, medicine & occupational health. Volume 2 of Handbook of Elemental Speciation], John Wiley and Sons, 2005, {{ISBN|0-470-85598-3}} p. 553</ref>

Between 70&nbsp;K and room temperature, berkelium behaves as a [[Curie–Weiss law|Curie–Weiss]] paramagnetic material with an effective magnetic moment of 9.69&nbsp;[[Bohr magneton]]s (μ<sub>B</sub>) and a [[Curie temperature]] of 101&nbsp;K. This magnetic moment is almost equal to the theoretical value of 9.72&nbsp;μ<sub>B</sub> calculated within the simple atomic [[Angular momentum coupling|L-S coupling model]]. Upon cooling to about 34&nbsp;K, berkelium undergoes a transition to an [[antiferromagnetism|antiferromagnetic]] state.{{sfn|Peterson|Hobart|1984|p=45}} The [[Enthalpy change of solution|enthalpy of dissolution]] in [[hydrochloric acid]] at standard conditions is −600&nbsp;kJ/mol, from which the [[standard enthalpy of formation]] (Δ<sub>f</sub>''H''°) of aqueous {{chem2|Bk(3+)}} ions is obtained as −601&nbsp;kJ/mol. The [[standard electrode potential]] {{chem2|Bk(3+)}}/Bk is −2.01&nbsp;V.<ref>{{cite journal|last1=Fuger|first1=J.|title=A new determination of the enthalpy of solution of berkelium metal and the standard enthalpy of formation of Bk3+ (aq)|journal=Journal of Inorganic and Nuclear Chemistry|volume=43|pages=3209|date=1981|doi=10.1016/0022-1902(81)80090-5|issue=12|last2=Haire|first2=R. G.|last3=Peterson|first3=J. R.}}</ref> The [[Ionization energy|ionization potential]] of a neutral berkelium atom is 6.23&nbsp;eV.{{sfn|Peterson|Hobart|1984|p=34}}