THE Laurentius is the chemical element of atomic number 113 of the Periodic Table. Because it is quite unstable, it is not possible to obtain it from natural sources, being necessary to synthesize it in the laboratory. Its production occurs through fusion reactions between an accelerated ion and another heavier atom. What are remarkable about the properties of Laurentium are its oxidation state equal to +3 in aqueous solutions and the fact that it finishes its eletronic distribution in 7s2 5f14 7p1, instead of 7s2 5f14 6d1.
Laurentium was first produced in 1961 at Berkeley laboratories in California, United States. Afterwards, its structure and other isotopes were elucidated with the collaboration of the Joint Institute for Nuclear Research, in the city of Dubna, Russia.
Its name refers to scientist Ernest Orlando Lawrence, creator of the cyclotron particle accelerator. A polemic about Laurentius is about his position in the Periodic table. Some argue that it should be in group 3, while other scientists argue that it shouldn't.
See too: Dubnium — the synthetic element named after the Russian city of Dubna
Summary about Laurentius
Laurentium is the last actinide in the Periodic Table.
It is a chemical element not found in nature, having to be produced in the laboratory, that is, it is a synthetic chemical element.
The most stable isotope of Laurentium is 262lr, with time half life of 3.6 hours.
Despite being a metal, its metallic form has never been obtained in the laboratory.
It is produced through fusion reactions, using a Particles accelerator.
It was discovered in 1961 in the laboratories of Berkeley, California, USA.
Its name refers to scientist Ernest Orlando Lawrence, creator of the cyclotron particle accelerator.
Laurence's properties
Symbol: lr
Atomic number: 103
Atomic mass: 262 c.u.
Electronic configuration: [Rn] 7s2 5f14 7p1
Most stable isotope: 262Lr (3.6 hour half-life)
Chemical series: group 3, f-block elements, actinides, metal, superheavy elements
Features of Laurentius
Laurentium, symbol Lr and atomic number 103, is a metal belonging to the actinide group. Elements such as Laurentium, due to the large number of protons and neutrons in the nucleus, are unstable, which means that the repulsive forces of the nucleus overcome the attractive forces.
Because of this, none of the 12 known isotopes of laurence are stable, with mass 262 having the longest half-life: 3.6 hours. Such instability does not allow obtaining laurence from natural sources, so that it is necessary to synthesize it in the laboratory to be studied and applied.
Despite being a metal, a metallic sample of laurence was never obtained. But, in solution, studies with this element have advanced, and it has already been proven that its state of oxidation more stable is +3, like the other actinides. This data even agrees with the predictions made by Glenn Seaborg, in 1949, about element 103.
Laurentius' chemistry, however, is quite peculiar. For example, its electronic distribution was expected to end in 7s2 5f14 6d1, however, it is observed that its configuration ends in 7s2 5f14 7p1.
This is a consequence of what we know as relativistic effect, a difference from what is observed to what was expected on account of relativity. When evaluating such an electronic distribution, it can be seen that the 7p sublevel of Laurentium is more stable than the 6d level.
All this complicates and greatly intensifies the lack of consensus on The region which The element belongs in the periodic table. This is because some researchers defend that he is in group 3, below scandium, yttrium and lutetium, because of the chemical similarity with them, based on data about Lr3+.
Others argue that Laurentium and Lutetium, because they have a complete f sublevel, should not be below the yttrium, but lanthanum (sixth period) and actinium (seventh period), since they have no f sublevel with electrons.
To resolve this issue, Iupac created, in December 2015, a study group to determine the constitution of group 3 of the Periodic Table. According to the institution, the work ended on the last day of 2021, and the last update is in April 2021. In it, the study group concluded that there is no objective way of judging the issue, and it is important for Iupac to speak out and determine a rule or convention.
For the authors, placing lutetium and laurence in group 3, pleases more, placing the elements in increasing order of atomic number, in addition to avoiding the division of the d-block if it is represented with 32 columns (version in which the series of lanthanides and actinides is included).
Obtaining Laurentius
As a synthetic element, The obtaining of Laurentius takes place in the laboratory with particle accelerators. Superheavy elements are commonly obtained in two ways: through fusion reactions or through the radioactive decay of another even heavier element. In the case of the most used isotopes of Laurentium, 256 and 260, the ways to obtain it are by Nuclear fusion, that is, two lighter nuclei merge into the laurence.
In the case of Laurentium-256, ions of 11B collide with atoms of 249Cf, forming the laurence and four more neutrons, according to the reaction:
\(\frac{249}{48}Cf+\frac{11}{5}B\rightarrow \frac{256}{103}Lr+4{_0^1}n\)
In a similar way, the 260Lr can be produced by fusion of ions 18O, accelerated towards a target of 249Bk, having as by-products an alpha particle and three more neutrons:
\(\frac{249}{97}Cf+{\frac{18}{8}}O\frac{260}{103}Lr+{_2^4}\alpha+3{_0^1}n\)
Check out our podcast: Particle accelerator: what is it and how does it work?
Precautions with Laurence
The time when the greatest amount of laurence was synthesized was in the 1970s, when 1500 atoms of it were produced for study. This means that the element, despite being radioactive, has minimal risk for not be produced on a large scale. Furthermore, in a controlled laboratory, these risks are anticipated and thus virtually controlled.
Laurence's story
![Entrance of Ernest Orlando Lawrence Berkeley National Laboratory, the laboratory that first produced Laurentium. [1]](/f/0e95834023b972833255f0ca3cce734f.jpg)
element 103 It was first produced in the year 1961, by US scientists led by Albert Ghiorso of Lawrence Berkeley National Laboratory. On that occasion, several isotopes of californium, Cf, were bombarded with ions of boron, both of mass 10 and of mass 11. Alpha particle detectors pointed to a new eight-second half-life activity, which the scientists attributed to element 103.
Despite alpha emission, the short half-life made it difficult to identify the element. Furthermore, as the target was composed of a mixture of californium isotopes, whose masses ranged from 249 to 252, the identification of the mass of element 103 produced also became ambiguous. It was speculated that isotopes of element 103 with mass between 255 and 259 had been produced, with 257 being the highest yield.
In 1965, scientists at the Joint Institute for Nuclear Research in Dubna, Russia, reacted 18or with atoms of 243Am, also producing three isotopes of element 103, but with some conflicts and differences from those obtained at Berkeley previously.
However, new experiments by Berkeley labs reacted with ions of 14Huh 15No with 248cm and ions 11B and 10B with 249Cf, so that, in 1971, managed to prove a good part of the results obtained in the 1960s and they also concluded that the first isotope synthesized of element 103 was that of mass 258.
The name of element 103, Laurentius, makes a reference to scientist Ernest Orlando Lawrence, inventor of the cyclotron particle accelerator, and was given by the Berkeley researchers. They still initially proposed the symbol Lw, but in 1971, Iupac, despite having made the name laurêncio official, changed the symbol to Lr.
In 1992, however, the work of the Iupac Transfers Working Group re-evaluated the work of the Dubna and Berkeley groups on element 103. As a result, in 1997, they determined that the credit for the discovery of element 103 should be divided between the Americans and the Russians. However, the name was eventually accepted by both parties, remaining unchanged.
Exercises solved on Laurentius
question 1
Laurentium, symbol Lr and atomic number 103, cannot be found in nature and thus must be produced in the laboratory. Its most stable isotope has a mass number of 262. How many neutrons are present in Lr isotope 262?
A) 103
B) 262
C) 159
D) 365
E) 161
Resolution:
Alternative C
The number of neutrons can be calculated by the following formula:
A = Z + n
Where A is the mass number, Z is the atomic number (numerically equal to the number of protons) and n is the number of neutrons.
Substituting the values, we have:
262 = 103 + n
n = 262 - 103
n = 159
question 2
The half-life of the most stable isotope of the chemical element Laurentium (Lr, Z = 103) is 3.6 hours. How long, in hours, does it take for the mass of this isotope to be 1/8 of its initial mass?
A) 3.6 hours
B) 7.2 hours
C) 10.8 hours
D) 14.4 hours
E) 18.0 hours
Resolution:
Alternative C
At each half-life, the amount of Lr drops by half. Thus, we assume that the initial mass is equal to m. After a half-life (3.6 hours), the mass of Lr that remains is half, that is, m/2. After another 3.6 hours (totaling 7.2 hours), the mass becomes m/4. Now, with another 3.6 hours (10.8 hours in total), the mass (which is in m/4) halves again, making it m/8, i.e. 1/8 of the initial mass.
image credit
[1] DJSinop / shutterstock
By Stefano Araújo Novais
Chemistry teacher
