Transuranic elements

An overview on discovery, synthesis and properties of transuranic elements

1. SCS, M.G.University 27/10/2015 Ramesh PI

2. INTRODUCTION Of  the elements with atomic numbers 1 to  92 (U),  all can be found  in nature   All  of the elements with higher atomic  numbers   have been first discovered in the laboratory They all are radioactive with a half-life much shorter than the age of earth. The term transuranium elements usually include the elements after Uranium (Neptunium onwards). The chemical and physical properties of these heavy elements are very difficult to study, due to high radioactivity and short life time.

3. DISCOVERY AND SYNTHESIS The first man-made transuranium element (Z=93) Discovered by McMillan and Abelson while studying the neutron-induced fission of uranium Neptunium was named after the planet Neptune the next after Uranus The reaction was 239 Np having a half life of 2.36 days. The most stable isotope is 237 Np (t 1/2 =2.14×10 6 years) Neptunium (Np) 238 U(n, γ ) 239 U 239 Np β - β - 23 m 2.3 d

4. Plutonium (Pu) Plutonium (Z=94) is the second transuranium element, was discovered by Seaborg The first isotope of Pu was synthesized by using 60 inch cyclotron in the deuteron bombardment of U. 238 Pu having a half-life of 87.7 years. 239 Pu is another isotope synthesized by β decay of 239 Np, with a half-life of 24000 y. This isotope is produced in nuclear reactors in appreciable amount. Which is of major importance because of its large fission cross section with thermal neutrons. It was named after the Pluto in analogy to U and Np. 238 U (d, 2n) 238 Np 238 Pu β - β - 2.1 d 87.7 y

5. Americium (Am) and Curium (Cm) Element 95, americium (Am), and element 96, Curium (Cm) were synthesized by seaborg and Ghiorso as follows The isotope 242 Cm was identified by observing the known isotope 238 Pu as the –decay daughter of the new isotope. 241 Am was produced trough the successive neutron capture reaction in 239 Pu. Both of these elements are quit similar to the rare earth elements in their chemical properties, with a stable oxidation state of 3+ It is too difficult to separate from each other and from rare earth elements. Half life of 241 Am is 432 days and that of 242 Cm is 163 days. 239 Pu(n, γ ) 240 Pu(n, γ ) 241 Pu 241 Am 239 Pu( α , n) 242 Cm 238 Pu β - β - α 163 d

6. Berkelium (Bk) and Californium ( Cf ) The element with atomic number 97, berkelium (Bk), was produced in irradiation of milligram amounts of 241 Am with α particles. The most stable isotope of Bk is 247 Bk having a half life 1380 y. I t decays to 243 Bk, through α emission, of half life 4.5 h. Californium ( Cf ) was synthesized in 1950 by irradiation of a few micrograms of 242 Cm with α particles, 245 Cf having half life 44 min. longest lived is 251 Cf with a t 1/2 of 900 y. The last four actinides (Am ,Cm, Bk and Cf ) all having 3+ as their most stable valance state in solution, like rare earth elements. 241 Am( α ,2n) 243 Bk EC. α 4.5 h 242 Cm( α , n) 245 Cf α ,EC 44 min

7. Einsteinium ( Es ) Einsteinium (Z=99) was discovered in 1952 by Albert Ghiorso and co-workers at the University of California, Berkeley, as a component of the debris of the first hydrogen bomb explosion, and named after Albert Einstein. Its most common isotope is 253 Es of t 1/2 20.47 days. It is produced from decay of 253 Cf in a few dedicated high-power nuclear reactors with a total yield on the order of one milligram per year. The most stable isotope 255 Es has a half life of 471.7 days. 238 U 253 Cf 253 Es +15n β - 6 β -

8. Fermium ( Fm ) Fermium (Z=100) is also identified in 1952 with Einsteinium in the same debris from the Mike thermonuclear explosion, and named after Enrico Fermi. A total of 19 isotopes are known, with  257 Fm being the longest-lived with a half-life of 100.5 days . It is the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities, although pure fermium metal has not yet been prepared The first isotope of 250 Fm (t 1/2 =30 minutes) is produced by bombarding a 238 U target with oxygen-16 ions, is done by a group at the Nobel Institute for physics in Stockholm.

9. Mendelevium ( Md ) Mendelevium (Z= 101) was produced in 1955 by irradiation of 253 Es with α particles. It is the first element that currently cannot be produced in macroscopic quantities. It can only be produced in particle accelerators by bombarding lighter elements with charged particles A total of sixteen mendelevium isotopes are known, the most stable being 258 Md with a half-life of 51 days. Mendelevium was discovered by bombarding einsteinium with alpha particles in 1955, the same method still used to produce it today It was named after Dmitri Mendeleev, father of the periodic table of the chemical elements.

10. Nobelium (No) First report of the discovery of the element 102 came from the Nobel Institute, Stockholm, Sweden. 246 No was produced in the following reaction by use of the double recoil technique, A total of twelve nobelium isotopes are known to exist; the most stable is 259 No with a half-life of 58 minutes, but the short lived 255 No (t 1/2 3.1 minutes) is most commonly used. In solution +2 oxidation state is more stable than +3 oxidation state The element was named Nobelium after Alfred Nobel. 246 Cm( 12 C, 4n) 254 No 250 Fm α α T 1/2 =3s 30 min

11. Lawrencium (Lr) The first identification of an isotope of element 103 was conducted by the Bekeley group in 1961. Which is named after Earnest O. Lawrence, inventor of cyclotron. Twelve isotopes of lawrencium are currently known; the most stable is 266 Lr with a half-life of 11 hours. B ut the shorter lived 260 Lr(t 1/2 2.7 minutes) is more in common use. The californium isotopes, 249,250,251,252 Cf, were bombarded with boron beams from the Heavy Ion Linear Accelerator (HILAC) : The Berkeley team reported that the isotope 258 Lr was detected in this manner, and that it decayed by emitting an 8.6 MeV alpha particle with a half-life of (8 ± 2) s The ion exchange experiments of 256 Lr (t 1/2 = 30s) confirmed that Lr exhibits a stable 3+ state in solution as expected. 249,250,251,252 Cf( 10,11 B, xn ) 258 Lr α 4.3 s

12. Rutherfordium (Rf ) It is the first element of transactinides, with atomic number 104 Rutherfordium was reportedly first detected in 1964 at the Joint Institute of Nuclear Research at Dubna (then in the Soviet Union ) Researchers there bombarded a plutonium-242 target with neon-22 ions Rutherfordium has no stable or naturally-occurring isotopes . Out of isotopes whose half-lives are known, the lighter isotopes usually have shorter half-lives; half-lives of under 50 μs for 253 Rf and 254 Rf were observed . The heaviest isotopes are the most stable, with  267 Rf having a measured half-life of about 1.3 h. Rutherfordium's basic properties will resemble those of other group 4 elements, so stable oxidation state in solution is +4. 242 Pu + 22 Ne 264-x Rf

13. The other transactinide elements are all very radioactive and having very short half life. So the scientific community could learn few properties of those elements in certain. So there are currently no uses for those, outside of basic scientific research. The elements from 114 to 118 synthesized would be in the successive 7p electron series, although the discoveries of the elements with Z>112 are still waiting to be confirmed

14. Actinides 93  neptunium  Np 94  plutonium  Pu 95  americium  Am 96  curium  Cm 97  berkelium  Bk 98  californium   Cf 99  einsteinium   Es 100  fermium   Fm 101  mendelevium   Md 102  nobelium  No 103  lawrencium  Lr Transactinide elements 104  rutherfordium   Rf 105  dubnium   Db 106  seaborgium   Sg 107  bohrium   Bh 108  hassium  Hs 109  meitnerium  Mt 110  darmstadtium  Ds 111  roentgenium   Rg 112  copernicium  Cn 113  ununtrium   Uut * 114  flerovium   Fl 115  ununpentium   Uup 116  livermorium   Lv 117  ununseptium   Uus * 118  ununoctium   Uuo * Period 8 elements none yet discovered. *The existence of these elements has been claimed and generally accepted, but not yet acknowledged by the IUPAC List of All Transuranic Elements

15. REFERENCE Production and properties of transuranium elements; By Y.Nagame * and M.Hirata ; Radiochim . Acta 99, 1-17 (2011) . https://en.wikipedia.org/wiki/Transuranium_element https://en.wikipedia.org/wiki Thank You…