Nobelium

mendelevium ← nobelium → lawrencium Yb ↑ No ↓ (Upb) 102No Periodic table
Appearance
unknown
General properties
Name, symbol, number	nobelium, No, 102
Pronunciation	/noʊˈbɛliəm/ noh-bel-ee-əm or /noʊˈbiːliəm/ noh-bee-lee-əm
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	[259]
Electron configuration	[Rn] 5f14 7s2
Electrons per shell	2, 8, 18, 32, 32, 8, 2 (Image)
Physical properties
Phase	solid
Atomic properties
Oxidation states	2, 3
Ionization energies	1st: 641.6 kJ·mol−1
	2nd: 1254.3 kJ·mol−1
	3rd: 2605.1 kJ·mol−1
Miscellanea
CAS registry number	10028-14-5
Most stable isotopes
Main article: Isotopes of nobelium
iso NA half-life DM DE (MeV) DP 262No syn 5 ms SF 260No syn 106 ms SF 259No syn 58m 75% α 7.69,7.61,7.53.... 255Fm 25% ε 259Md 258No syn 1.2 ms SF 257No syn 25 s α 8.32,8.22 253Fm 256No syn 2.91 s 99.5% α 8.45,8.40 252Fm 0.5% f 255No syn 3.1 m 61% α 8.12,8.08,7.93 251Fm 39% ε 2.012 255Md 254Nom2 syn 198 µs γ 254Nom1 254Nom1 syn 275 ms γ 250Nog 254Nog syn 51 s 253Nom syn 43.5 µs γ 253Nog 253No syn 1.62 m α 8.14,8.06,8.04,8.01 249Fm 252Nom syn 110 ms 252Nog syn 2.44 s 75% α 8.42,8.37 248Fm 25% SF 251No syn 0.76 s α 8.62,8.58 247Fm 250Nom syn 43 µs SF 250Nog syn 3.7 µs SF
v ·		Nobelium Common English pronunciation of nobelium
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Nobelium ( /noʊˈbɛliəm/ noh-bel-ee-əm or /noʊˈbiːliəm/ noh-bee-lee-əm) is a synthetic element with the symbol No and atomic number 102. It was first correctly identified in 1966 by scientists at the Flerov Laboratory of Nuclear Reactions in Dubna, Soviet Union. Little is known about the element but limited chemical experiments have shown that it forms a stable divalent ion in solution as well as the predicted trivalent ion that is associated with its presence as one of the actinoids.

Discovery profile

The discovery of element 102 was first announced by physicists at the Nobel Institute in Sweden in 1957. The team reported that they created an isotope with a half-life of 10 minutes, decaying by emission of an 8.5 MeV alpha particle, after bombarding ²⁴⁴Cm with ¹³C nuclei. The activity was assigned to ²⁵¹No or ²⁵³No. The scientists proposed the name nobelium (No) for the new element. Later they retracted their claim and associated the activity to background effects.

The synthesis of element 102 was then claimed in April 1958 at the University of California, Berkeley by Albert Ghiorso, Glenn T. Seaborg, John R. Walton and Torbjørn Sikkeland. The team used the new heavy-ion linear accelerator (HILAC) to bombard a curium target (95% ²⁴⁴Cm and 5% ²⁴⁶Cm) with ¹³C and ¹²C ions. They were unable to confirm the 8.5 MeV activity claimed by the Swedes but were instead able to detect decays from ²⁵⁰Fm, supposedly the daughter of ²⁵⁴102, which had an apparent half-life of ~3 s. In 1959 the team continued their studies and claimed that they were able to produce an isotope that decayed predominantly by emission of an 8.3 MeV alpha particle, with a half-life of 3 s with an associated 30% spontaneous fission branch. The activity was initially assigned to ²⁵⁴No but later changed to ²⁵²No. The Berkeley team decided to adopt the name nobelium for the element.

244
96Cm + 12
6C → 256
102No*
→ 252
102No + 4 1
0n

Further work in 1961 on the attempted synthesis of element 103 produced evidence for a Z=102 alpha activity decaying by emission of an 8.2 MeV particle with a half-life of 15 s, and assigned to ²⁵⁵No.

Following initial work between 1958–1964, in 1966, a team at the Flerov Laboratory of Nuclear Reactions (FLNR) reported that they had been able to detect ²⁵⁰Fm from the decay of a parent nucleus (²⁵⁴No) with a half-life of ~50s, in contradiction to the Berkeley claim. Furthermore, they were able to show that the parent decayed by emission of 8.1 MeV alpha particles with a half-life of ~35 s.

238
92U + 22
10Ne → 260
102No*
→ 254
102No + 6 1
0n

In 1969, the Dubna team carried out chemical experiments on element 102 and concluded that it behaved as the heavier homologue of ytterbium. The Russian scientists proposed the name joliotium (Jo) for the new element.

Later work in 1967 at Berkeley and 1971 at Oak Ridge fully confirmed the discovery of element 102 and clarified earlier observations.

In 1992, the IUPAC-IUPAP Transfermium Working Group (TWG) assessed the claims of discovery and concluded that only the Dubna work from 1966 correctly detected and assigned decays to Z=102 nuclei at the time. The Dubna team are therefore officially recognised as the discoverers of nobelium although it is possible that it was detected at Berkeley in 1959.

Naming

Element 102 was first named nobelium (No) by its claimed discoverers in 1957 by scientists at the Nobel Institute in Sweden. The name was later adopted by Berkeley scientists who claimed its discovery in 1959.

The International Union of Pure and Applied Chemistry (IUPAC) officially recognised the name nobelium following the Berkeley results.

In 1994, and subsequently in 1997, the IUPAC ratified the name nobelium (No) for the element on the basis that it had become entrenched in the literature over the course of 30 years and that Alfred Nobel should be commemorated in this fashion.^{[citation needed]}

Physical properties

The appearance of this element is unknown, however it is most likely silvery-white or gray and metallic. If sufficient amounts of nobelium were produced, it would pose a radiation hazard. Some sources quote a melting point of 827 °C for nobelium but this cannot be substantiated from an official source and seems implausible regarding the requirements of such a measurement. However, the 1st, 2nd and 3rd ionization energies have been measured^{[citation needed]}. In addition, an electronegativity value of 1.3 is also sometimes quoted. This is most definitely only an estimate since a true value can only be determined using a chemical compound of the element and no such compounds exist for nobelium.

Experimental chemistry

Aqueous phase chemistry

First experiments involving nobelium assumed that it predominantly formed a +III state like earlier actinoids. However, it was later found that nobelium forms a stable +II state in solution, although it can be oxidised to an oxidising +III state.^[1] A reduction potential of −1.78 V has been measured for the No³⁺ ion. The hexaaquanobelium(II) ion has been determined to have an ionic radius of 110 pm.

Summary of compounds and (complex) ions

Formula	Names(s)
[No(H2O)6]3+	hexaaquanobelium(III)
[No(H2O)6]2+	hexaaquanobelium(II)

Isotopes

Main article: Isotopes of nobelium

Twelve radioisotopes of nobelium have been characterized, with the most stable being ²⁵⁹No with a half-life of 58 minutes. Longer half-lives are expected for the as-yet-unknown ²⁶¹No and ²⁶³No. An isomeric level has been found in ²⁵³No and K-isomers have been found in ²⁵⁰No, ²⁵²No and ²⁵⁴No to date.

Synthesis of isotopes as decay products

Isotopes of nobelium have also been identified in the decay of heavier elements. Observations to date are summarised in the table below:

Evaporation Residue	Observed No isotope
262Lr	262No
269Hs, 265Sg, 261Rf	257No
267Hs, 263Sg, 259Rf	255No
254Lr	254No
261Sg, 257Rf	253No
264Hs, 260Sg, 256Rf	252No
255Rf	251No

Chronology of isotope discovery

Isotope	Year discovered	Discovery reaction
250Nom	2001	204Pb(48Ca,2n)
250Nog	2006	204Pb(48Ca,2n)
251No	1967	244Cm(12C,5n)
252Nog	1959	244Cm(12C,4n)
252Nom	~2002	206Pb(48Ca,2n)
253Nog	1967	242Pu(16O,5n),239Pu(18O,4n)
253Nom	1971	249Cf(12C,4n)
254Nog	1966	243Am(15N,4n)
254Nom1	1967?	246Cm(13C,5n),246Cm(12C,4n)
254Nom2	~2003	208Pb(48Ca,2n)
255No	1967	246Cm(13C,4n),248Cm(12C,5n)
256No	1967	248Cm(12C,4n),248Cm(13C,5n)
257No	1961? , 1967	248Cm(13C,4n)
258No	1967	248Cm(13C,3n)
259No	1973	248Cm(18O,α3n)
260No	?	254Es + 22Ne,18O,13C - transfer
261No	unknown
262No	1988	254Es + 22Ne - transfer (EC of 262Lr)

Isomerism in nobelium nuclides

²⁵⁴No The study of K-isomerism was recently studied by physicists at the University of Jyväskylä physics laboratory (JYFL). They were able to confirm a previously reported K-isomer and detected a second K-isomer. They assigned spins and parities of 8^- and 16⁺ to the two K-isomers.

²⁵³No In 1971, Bemis et al. was able to determine an isomeric level decaying with a half-life of 31 µs from the decay of ²⁵⁷Rf. This was confirmed in 2003 at the GSI by also studying the decay of ²⁵⁷Rf. Further support in the same year from the FLNR appeared with a slightly higher half-life of 43.5 µs, decaying by M2 gamma emission to the ground state.

²⁵²No In a recent study by the GSI into K-isomerism in even-even isotopes, a K-isomer with a half-life of 110 ms was detected for ²⁵²No. A spin and parity of 8^- was assigned to the isomer.

²⁵⁰No In 2003, scientists at the FLNR reported that they had been able to synthesise ²⁴⁹No which decayed by SF with a half-life of 54µs. Further work in 2006 by scientists at the ANL showed that the activity was actually due to a K-isomer in ²⁵⁰No. The ground state isomer was also detected with a very short half-life of 3.7µs.

Chemical yields of isotopes

Cold fusion

The table below provides cross-sections and excitation energies for cold fusion reactions producing nobelium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Projectile	Target	CN	1n	2n	3n	4n
48Ca	208Pb	256No		254No: 2050 nb ; 22.3 MeV
48Ca	207Pb	255No		253No: 1310 nb ; 22.4 MeV
48Ca	206Pb	254No	253No: 58 nb ; 23.6 MeV	252No: 515 nb ; 23.3 MeV	251No: 30 nb ; 30.7 MeV	250No: 260 pb ; 43.9 MeV
48Ca	204Pb	252No		250No:13.2 nb ; 23.2 MeV

Hot fusion

The table below provides cross-sections and excitation energies for hot fusion reactions producing nobelium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Projectile	Target	CN	3n	4n	5n	6n
26Mg	232Th	258No		254No:1.6 nb	253No:9 nb	252No:8 nb
22Ne	238U	260No		256No:40 nb	255No:200 nb	254No:15 nb
22Ne	236U	258No		254No:7 nb	253No:25 nb	252No:15 nb

Retracted isotopes

In 2003, scientists at the FLNR claimed to have discovered the lightest known isotope of nobelium. However, subsequent work showed that the 54 µs activity was actually due to ²⁵⁰No and the isotope ²⁴⁹No was retracted.

References

1. ^ Toyoshima, A.; Kasamatsu, Y.; Tsukada, K.; Asai, M.; Kitatsuji, Y.; Ishii, Y.; Toume, H.; Nishinaka, I. et al. (Jul 2009). "Oxidation of Element 102, Nobelium, with Flow Electrolytic Column Chromatography on an Atom-at-a-Time Scale". Journal of the American Chemical Society 131 (26): 090610145759060. doi:10.1021/ja9030038. ISSN 0002-7863. PMID 19514720.  edit

Notes

• Los Alamos National Laboratory - Nobelium
• Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
• It's Elemental - Nobelium

External links

• WebElements.com - Nobelium