NUCLEAR CHEMISTRY: HISTORY, FIELD OF STUDY, AREAS, APPLICATIONS - CHEMISTRY - 2025

The nuclear chemistry is the study of changes in the product properties of matter phenomena occurred in nuclei of atoms; it does not study the way its electrons interact or their bonds with other atoms of the same or a different element.

This branch of chemistry then focuses on the nuclei and the energies released when they add or lose some of their particles; which are called nucleons, and which for chemical purposes essentially consist of protons and neutrons.

Radioactive clover. Source: Pixabay.

Many nuclear reactions consist of a change in the number of protons and / or neutrons, which has as a consequence the transformation of one element into another; ancient dream of the alchemists, who tried in vain to turn lead metal into gold.

This is perhaps the most surprising characteristic of nuclear reactions. However, such transformations release enormous amounts of energy, as well as accelerated particles that manage to penetrate and destroy the matter around them (such as the DNA of our cells) depending on their associated energy.

That is, in a nuclear reaction different types of radiation are released, and when an atom or isotope releases radiation, it is said to be radioactive (radionuclides). Some radiation can be harmless, and even benign, used to fight cancer cells or study the pharmacological effect of certain drugs by radioactive labeling.

Other radiations, on the other hand, are destructive and deadly at minimum contact. Unfortunately, several of the worst catastrophes in history carry the symbol of radioactivity (radioactive clover, top image).

From nuclear weapons, to the Chernobyl episodes and the misfortune of radioactive waste and its effects on wildlife, there are many disasters triggered by nuclear energy. But, on the other hand, nuclear energy would guarantee independence from other energy sources and the pollution problems they cause.

It would (probably) be clean energy, capable of powering cities for an eternity, and the technology would exceed its earthly limits.

To achieve all this at the lowest human (and planetary) cost, scientific, technological, ecological, and political programs and efforts are needed to “tame” and “mimic” nuclear energy in a safe and beneficial way for humanity and its growth. energetic.

History of nuclear chemistry

Dawn

Leaving the alchemists and their philosopher's stone in the past (although their efforts have borne fruit of vital importance for the understanding of chemistry), nuclear chemistry was born when what is known as radioactivity was first detected.

It all started with the discovery of X-rays by Wilhelm Conrad Röntgen (1895), at the University of Wurzburg. He was studying cathode rays when he noticed that they originated a strange fluorescence, even with the device turned off, capable of penetrating the opaque black paper that covered the tubes in which the experiments were carried out.

Henri Becquerel, motivated by the discoveries of X-rays, designed his own experiments to study them using fluorescent salts, which darkened photographic plates, protected by black paper, when they were excited by sunlight.

It was found accidentally (since the weather in Paris was cloudy at that time), that uranium salts obscured photographic plates, regardless of the light source that fell on them. He then concluded that he had found a new type of radiation: radioactivity.

Jobs of the Curie spouses

Becquerel's work served as a source of inspiration for Marie Curie and Pierre Curie to delve into the phenomenon of radioactivity (a term coined by Marie Curie).

Thus, they looked for other minerals (in addition to uranium) that also presented this property, finding that the mineral pitchblende is even more radioactive, and that therefore, it must have other radioactive substances. How? By comparing the electrical currents generated by the ionization of gas molecules around the samples.

After years of arduous extraction work and radiometric measurements, he extracted the radioactive elements radium (100 mg from a 2000 kg sample) and polonium from the mineral pitchblende. Also, Curie determined the radioactivity of the element thorium.

Unfortunately, by then the harmful effects of such radiation were beginning to be discovered.

Measurements of radioactivity were facilitated with the development of the Geiger counter (having Hans Geiger as a co-inventor of the artifact).

Nucleus fractionation

Ernest Rutherford observed that each radioisotope had its own decay time, independent of temperature, and that it varied with the concentration and characteristics of the nuclei.

It also demonstrated that these radioactive decays obey first-order kinetics, whose half-lives (t _1/2) are still very useful today. Thus, each substance that emits radioactivity has a different t _1/2, which ranges from seconds, days, to millions of years.

In addition to all the above, he proposed an atomic model as a result of the results of his experiments irradiating a very thin sheet of gold with alpha particles (helium nuclei). Working again with the alpha particles, he achieved the transmutation of nitrogen atoms to oxygen atoms; in other words, he had managed to convert one element into another.

In doing so, it was shown at once that the atom was not indivisible, and even less when it was bombarded by accelerated particles and "slow" neutrons.

Field of study

Practice and theory

Those who decide to become part of the nuclear chemistry specialists can choose from several fields of study or research, as well as different fields of work. Like many branches of science, they can be devoted to practice, or theory (or both at the same time) in their corresponding fields.

A cinematic example is seen in superhero movies, where scientists get an individual to acquire super powers (such as the Hulk, the fantastic four, Spiderman, and Doctor Manhattan).

In real life (superficially at least), nuclear chemists instead seek to design new materials capable of withstanding enormous nuclear resistance.

These materials, like the instrumentation, must be indestructible and special enough to isolate the emission of radiation and the enormous temperatures unleashed when initiating nuclear reactions; especially those of nuclear fusion.

In theory, they can design simulations to first estimate the feasibility of certain projects and how to improve them at the lowest cost and negative impact; or mathematical models that allow to unravel the pending mysteries of the nucleus.

Likewise, they study and propose ways to store and / or treat nuclear waste, since it takes billions of years to decompose and is highly polluting.

Typical jobs

Here is a short list of typical jobs that a nuclear chemist can do:

-Direct research in government, industrial or academic laboratories.

-Process hundreds of data through statistical packages and multivariate analysis.

-They teach classes in universities.

-Develop safe radioactivity sources for various applications involving a general public, or for use in aerospace devices.

-Design techniques and devices that detect and monitor radioactivity in the environment.

-Guarantee that the laboratory conditions are optimal for handling radioactive material; which they even manipulate using robotic arms.

-As technicians, they maintain dosimeters and collect radioactive samples.

Areas

The previous section described in general terms what are the tasks of a nuclear chemist in his workplace. Now, a little more is specified about different areas in which the use or study of nuclear reactions is present.

Radiochemistry

In radiochemistry, the radiation process itself is studied. This means that it considers all radioisotopes in depth, as well as their decay time, the radiation they release (alpha, beta or gamma), their behavior in different environments, and their possible applications.

This is perhaps the area of ​​nuclear chemistry that has advanced the most today compared to the others. He has been in charge of using radioisotopes and moderate doses of radiation in an intelligent and friendly way.

Nuclear energy

In this area, nuclear chemists, together with researchers from other specialties, study and design safe and controllable methods to take advantage of nuclear energy produced by the fission of nuclei; that is, of its fractionation.

Likewise, it is proposed to do the same with nuclear fusion reactions, such as those who would like to tame small stars that provide their energy; with the impediment that the conditions are overwhelming and there is no physical material capable of resisting them (imagine enclosing the sun in a cage that does not melt due to the intense heat).

Nuclear power may well be used for charitable purposes, or for war purposes, in developing more weapons.

Storage and waste

The problem that nuclear waste represents is very serious and threatening. It is for this reason that in this area they are dedicated to devising strategies to "imprison them" in such a way that the radiation they emit does not penetrate their containment shell; shell, which must be able to withstand earthquakes, floods, high pressures and temperatures, etc.

Artificial radioactivity

All transuranic elements are radioactive. They have been synthesized using different techniques, including: the bombardment of nuclei with neutrons or other accelerated particles.

For this, use has been made of linear accelerators or cyclotrons (which are D-shaped). Inside them, the particles are accelerated to speeds close to those of light (300,000 km / s), and then collide with a target.

Thus, several artificial, radioactive elements were born, and their abundance on Earth is nil (although they may exist naturally in regions of the Cosmos).

In some accelerators the power of collisions is such that a disintegration of matter occurs. By analyzing the fragments, which can hardly be detected due to their short lifespan, it has been possible to learn more about the compendium of atomic particles.

Applications

Cooling towers of a nuclear power plant. Source: Pixabay.

The image above shows two cooling towers characteristic of nuclear power plants, whose plant can supply an entire city with electricity; for example, the Springfield plant, where Homer Simpson works, and owned by Mr. Burns.

Then, nuclear power plants use the energy released from nuclear reactors to supply an energy need. This is the ideal and promising application of nuclear chemistry: unlimited energy.

Throughout the article, mention has been made, implicitly, of numerous applications of nuclear chemistry. Other applications not so obvious, but that are present in daily life, are the following below.

Medicine

One technique for sterilizing surgical material is to irradiate it with gamma radiation. This completely destroys the microorganisms that they may harbor. The process is cold, so certain biological materials, sensitive to high temperatures, can also be subjected to such radiation doses.

The pharmacological effect, distribution and elimination of the new drugs is evaluated through the use of radioisotopes. With an emitted radiation detector, you can have a real picture of the distribution of the drug in the body.

This image makes it possible to determine how long the drug acts on a certain tissue; if it fails to absorb properly, or if it remains indoors for longer than is adequate.

Food preservation

Similarly, stored food can be irradiated with a moderate dose of gamma radiation. This is responsible for eliminating and destroying bacteria, keeping food edible for a longer time.

For example, a package of strawberries can be kept fresh after even 15 days of storage using this technique. The radiation is so weak that it does not penetrate the surface of the strawberries; and therefore, they are not contaminated, nor do they become "radioactive strawberries".

Smoke detectors

Inside the smoke detectors is only a few milligrams of americium (²⁴¹ Am). This radioactive metal at these amounts exhibits radiation harmless to people present under the roofs.

The ²⁴¹ Am emits low energy alpha particles and gamma rays, these rays being able to escape the detector. Alpha particles ionize the oxygen and nitrogen molecules in the air. Inside the detector, a voltage difference collects and orders the ions, producing a slight electrical current.

The ions end up at different electrodes. When smoke enters the detector's internal chamber, it absorbs alpha particles and ionization of the air is disrupted. Consequently, the electric current is stopped and an alarm is activated.

Elimination of pests

In agriculture, moderate radiation has been used to kill undesirable insects on crops. Thus, the use of highly polluting insecticides is avoided. This reduces the negative impact on soils, groundwater and the crops themselves.

Dating

With the help of radioisotopes, the age of certain objects can be determined. In archaeological studies this is of great interest since it allows the samples to be separated and placed in their corresponding times. The radioisotope used for this application is carbon 14 (¹⁴ C) par excellence. Its t _1/2 is 5700 years, and samples can be dated up to 50,000 years old.

The decay of ¹⁴ C has been used especially for biological samples, skeletons, fossils, etc. Other radioisotopes, such as ²⁴⁸ U, are t _1/2 million years old. By then measuring the concentrations of ²⁴⁸ U in a sample of meteorites, sediments and minerals, it can be determined whether it is the same age as Earth.

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