An overview on discovery, synthesis and properties of transuranic elements

1. TRANSURANIUM
ELEMENTS
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
239Np having a half life of 2.36 days. The most stable isotope is 237Np
(t1/2=2.14×106 years)
Neptunium (Np)
238U(n,γ)239U 239Np
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.
 238Pu having a half-life of 87.7 years.
 239Pu is another isotope synthesized by β decay of 239Np, 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.
238U (d, 2n)238Np 238Pu
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 242Cm was identified by observing the known isotope 238Pu as
the –decay daughter of the new isotope.
 241Am was produced trough the successive neutron capture reaction in
239Pu.
 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 241Am is 432 days and that of 242Cm is 163 days.
239Pu(n,γ)240Pu(n,γ)241Pu 241Am
239Pu(α, n)242Cm 238Pu
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 241Am with α particles.
 The most stable isotope of Bk is 247Bk having a half life 1380 y. It
decays to 243Bk, through α emission, of half life 4.5 h.
 Californium (Cf) was synthesized in 1950 by irradiation of a few
micrograms of 242Cm with α particles,
 245Cf having half life 44 min. longest lived is 251Cf with a t1/2 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.
241Am(α,2n) 243Bk
EC.α
4.5 h
242Cm(α, n)245Cf
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 253Es of t1/2 20.47 days.
 It is produced from decay of 253Cf in a few dedicated high-power
nuclear reactors with a total yield on the order of one milligram
per year.
 The most stable isotope 255Es has a half life of 471.7 days.
238U 253Cf 253Es
+15n β -
6β -

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 257Fm 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 250Fm (t1/2 =30 minutes) is produced by
bombarding a 238U 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 253Es
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 258Md 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.
 246No 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 259No with a half-life of 58 minutes, but the short lived
255No (t1/2 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.
246Cm(12C, 4n)254No 250Fm
α α
T1/2=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 266Lr with a half-life of 11 hours. But the shorter lived
260Lr(t1/2 2.7 minutes) is more in common use.
 The californium isotopes, 249,250,251,252Cf, were bombarded with
boron beams from the Heavy Ion Linear Accelerator (HILAC) :
 The Berkeley team reported that the isotope 258Lr 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 256Lr (t1/2 = 30s) confirmed that Lr
exhibits a stable 3+ state in solution as expected.
249,250,251,252Cf(10,11B, xn)258Lr
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 253Rf and
254Rf were observed.
 The heaviest isotopes are the most stable, with 267Rf 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.
242Pu + 22Ne 264-xRf

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