What does make a radioactive element radioactive?

Rodolfo Marin Rivera

1The periodic table as we know contains 118 elements,

which are organised according to their atomic number, electron configuration, and chemical properties thanks to discovery done be Dmitri Mendeleev (1869). However, all of them may have some level of radioactivity.

As we know, atoms are made up of small, positively charged nucleus surrounded by a relatively large space (orbitals) occupied by tiny, fast-moving, negatively charged electrons, which are 10,000 to 100,000 times smaller than the atoms. Despite its relatively small size, the nucleus contains over 99.9% of the mass of the atom. A very close approximation about what is going on during the interaction between the electrons and nucleus was given by Bohr (1913) who depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus with attraction provided by electrostatic forces.


The nucleus is made of positively charged protons and neutral neutrons. The number of protons is equal to the atom atomic number and determines, for instance, what element it is. For example, an atom with 8 protons in its nucleus is an oxygen atom, the eight-element listed in the periodic table. The number of neutrons will simple affect the mass of the atom and determine which isotope of oxygen is. Therefore, every chemical element has one or more isotopes that, for a given element, the number of protons and neutrons may change or not. Isotopes are better known as nuclide. Nuclide refers to any isotope of any element, or in other words, a nucleus with any number of protons and neutrons. Therefore, the radioactivity of a certain element is given by the transformation of a certain nuclide, or by the intensity at which the nuclide may decay. This means that a radioactive nuclide is one that spontaneously undergoes nuclear decay.

3During nuclear reactions (as the big bang), the interaction between a particle (like a neutron) or a photon with a nucleus leads to the formation of another nuclide. This transformation is known as nuclear decay. A nuclear decay stars with an unstable nuclide (parent isotope) that typically spits out a particle and/or a photon while turning itself into something more stable. Therefore, energy is released as part of all nuclear decay. There are three different kinds of decay: alpha (i.e. ejection of neutrons and protons at once, formation of the helium atom), beta (ejection of electrons) and gamma (no particles are emitted or absorbed, and both the numbers of protons and neutrons remains the same). In this last type of decay, at the beginning, neutrons and protons are arranged poorly, in terms of energy. That is to say one or more neutrons/protons occupy a higher energy state than they need to, and that the nucleus is said to be in an excited state. Rearrangement allows the neutrons/protons that are in unusually high-energy states to drop down into lower ones. The lowest energy configuration would be called the ground state. Rearrangement from a higher energy state to a lower one requires the release of energy, which can be done in the form of a high-energy photon, or gamma ray.

Nowadays, about 20 radioactive nuclides are recognised, which will take a very long time to decay. One of the most notable is 40K. Since all isotopes of an element have the same chemical behaviour, and because we humans need potassium in our bodies, we all have some 40K in our bodies. Anything that contains potassium (bananas, Gatorade®, your friends) is naturally radioactive, i.e. of natural radioactive origin (also known as Naturally-Occurring Radioactive Materials, NORM).

All but three of these 20 long-lived radioactive nuclides decay to stable nuclides. The three that don’t are 232Th, 235U and 238U. They all eventually decay to stable isotopes of lead, but along the way, they produce a number of other naturally occurring radioactive nuclides (e.g., 222Rn).

4You must know that from all the ionizing radiation that exist around us, not all of them is related to our activities as human being, because radionuclides exist everywhere in nature (in soil and rocks, air and water, in plants and in our bodies). Some of the isotopes have been there since the creation of Earth, others are being constantly produced or brought in from outer space as cosmogenic radiation.

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Cell-sized robots that can change their shape

imagesResearchers at Cornell University built origami machines that can modify their shape in response to different stimuli and carry loads such as embedded electronics. These small robots are extremely small and are produced by graphene actuators that can fold 2D patterns into targeted 3D structures.

This research has no application for the moment, however it opens new paths to robotics for cells and biological systems.

Getting interested? Read more:



3D-Printing human tissues using cellulose: will science fiction become reality?

Carmen Piras

imagesMost of you have probably heard about the Frankenstein’s monster, a novel written by the English author Mary Shelley. For those who don’t know it, it is the story of Victor Frankenstein, a scientist who invented a secret technique to impart life to unanimated matter. This technique allowed him to create a monstrous creature with human emotions and sensations.

This is of course only science fiction. However, nowadays, the on-demand growth of human tissues and organs using artificial instruments is becoming reality. One emerging manufacturing technique with promise in tissue engineering and regenerative medicine is 3D printing, which is based on the 3D deposition of material in specific shapes. This technology can be applied in biology (3D bioprinting) to produce 3D scaffolds of our tissues. The cells are directly embedded inside the scaffolds and different cell types can be distributed in different locations. The material loaded with the cells is then 3D printed into the desired shape. This method allows the fabrication of bone and cartilage tissues, skin and cardiac constructs and the regeneration of hepatic tissue.

One of the most important factors in 3D bioprinting is the choice of the material used as ink (or, more specifically, bioink), which should be biocompatible and allow cell survival during the printing process. Beside this, the ink should have an optimal viscosity to allow printing and to avoid the 3D printed shape to collapse. Water based gels (also called hydrogels) are ideal inks for 3D bioprinting. These materials are mainly composed of water (> 99 %) and therefore can closely mimic the natural environment of cells.

Hydrogels can be obtained from a wide range of molecules including natural derivatives such as gelatine, alginate, collagen, hyaluronic acid and cellulose. Being an abundant, renewable, low-cost resource, cellulose represents an ideal candidate for the production of hydrogels for 3D bioprinting. This molecule is formed of long glucose chains and it is obtained by extraction from plants or can be produced by bacteria. Mechanical and chemical treatments of raw materials allow the extraction of cellulose in the form of nanofibers or nanocrystals. The suffix nano- refers to the fact that the extracts have one dimension (length or width) in the nanometre range (1.000.000 smaller than 1 mm).

UnknownA variety of bioinks based on cellulose nanofibers and nanocrystals has been created by a number of research groups. These could be applied for the regeneration of human tissues (such as cartilage) or to obtain 3D printed drug delivery systems and wound dressings. Although very promising, this research field is still new and growing. We hope that in the future cellulose will be further exploited to develop new bioinks. Will this be the route towards a new Frankenstein’s monster? Stay tuned!

Want to know more about this? Read this article: http://pubs.rsc.org/en/content/articlepdf/2017/bm/c7bm00510e




New polymers to store methane and capture CO2


Researchers at the University of Milano Bicocca recently published an interesting research on novel porous 3D polymers for methane storage and CO2 capture. These were based on aromatic building blocks connected to formed a big cross-linked network.

Read more about this study here!


New sensors: monitoring breath for kidney disease

UnknownCurious to see if you have a kidney disease in a very fast way? You can do it by just breathing!

Researchers at the University of Illinois have discovered a sensor based on a nonporous organic semiconductor thin film that can monitor the levels of ammonia in the breath. Since ammonia is a biomarker for chronic kidney disease, this highlights the importance of this research and its future impact in the development of novel health monitoring technologies.

Read the full article here!




The molecule of this week is theofylline, a methylxanthine that can be naturally found in cocoa beans. This molecule has a very similar chemical structure to other xanthines like caffeine or theobromine. However, it has pharmacological applications as it is used to treat asthma and other respiratory diseases.
Read more about theofylline here!


You probably heard before that doing chemistry is like cooking……BookCover

Well…It is also true that you can find some chemistry in your kitchen! To know more, read this interesting book by Matthew Hartings, who will explain you basic chemistry principles through simple recipes!
Read more here!