Acknowledgment
I would like to express my special thanks of gratitude to my school ( Birla public School,
Doha- Qatar) as well as our principal _______who gave me the golden opportunity to
do this wonderful chemistry project on nuclear chemistry, which also helped me in doing
a lot of Research and I came to know about so many new things. I am really thankful to
them.
Secondly, I would also like to thank my chemistry teacher ________ who helped me a
lot in finalizing this project within the limited time frame. He gave me all the important
information regarding the topic and helped me to understand the in-depth of the topic.
Lastly, I would like to thank the laboratory assistants and the lab technician to help me
conduct the experiments required by the topic for the project, and thank them for all the
support and guidance while conducting the experiments, their wisdom and
understanding of the lab equipment helped me to take precautions during the
experiments and I could successfully complete the experiments on time.
INDEX
Serial
Number
Topic
Page
Number
1.
Whats is Nuclear Chemistry
4
2.
Sources of radioactive elements
5
-Primordial
-Cosmogenic
-Anthropogenic
3.
Radiation and Nuclear Reactions
6
-Alpha
-Beta
-Gamma
4.
Half Life
9
5.
Stimulated Nuclear Reactions
11
-Nuclear fission
-Nuclear fusion
6.
Conclusion
14
7.
Bibliography
15
What is Nuclear Chemistry?
Chemical reactions happen when an atom’s outermost electrons undergo changes and
the proton and neutrons and even the inner electron shells are usually completely
unaffected. When protons and neutrons are directly involved in reactions, huge amounts
of energy can be released. Far more than by the transfer of electrons that occur in
simple chemical reactions. When changes happen to the nucleus of an atom we rather
logically call their study: Nuclear Chemistry.
All of these changes involve massive changes in energy. Energy changes which are
hundreds of thousands of times larger than in a typical chemical reaction. Because
these energy changes are so big we actually get a measurable change in the mass
between the products and the reactants.
Sources of Radioactive Elements
There are essentially three sources of radioactive elements:
1. PRIMORDIAL NUCLIDES
Primordial Nuclides commonly known as primordial Nuclides are one of the first atomic species
which ever came into existence. The term is quite self-explanatory as the word
‘Nuclides’ means an atomic species which is identified by a specific composition of the
nucleus whereas the word ‘primordial’ means ‘primeval ’.
These are presumed to have been formed after the Big Bang due to nucleosynthesis
between stars and supernovae. Nucleosynthesis is the process of creation of new
atomic nuclei from already pre-existing nuclei. Since these Nuclides came into
existence billions of years ago and yet have survived, they are said to be highly stable.
There are only 286 such Nuclides present
All of the 286 known primordial Nuclides have an exceptional half life which is quite
significant due to their existence. Cadmium, tellurium, xenon, neodymium, samarium
and uranium each have two primordial radioisotopes.
2. COSMOGENIC NUCLIDES
Cosmogenic nuclides are atoms that are constantly being amalgamated from the collision
of planetary surfaces by cosmic particles or rays (primarily protons ejected from the Sun).
3. ANTHROPOGENIC NUCLIDES
The last source of radioactive nuclides is called anthropogenic and is formed from
human activity in the formatiotion of nuclear power, nuclear weapons, or through the
use of particle accelerators.
RADIATION AND NUCLEAR REACTIONS
In 1902, Soddy proposed the idea that "radioactivity is the result of a natural change of
an isotope of 1 element into an isotope of a different element." Nuclear reactions involve
changes in particles in an atom's nucleus and thus cause a change within the atom
itself. All elements that weigh more than bismuth (and some lighter) showcase a
tendency of radioactivity and thus can "decay" into lighter elements. Unlike standard
chemical reactions that combine to form molecules, nuclear reactions end in the
transmutation of 1 element into a different isotope or a different element as a whole
(remember that the number of protons in an atom defines the element, so a distortion in
the number of protons leads to a change within the atom).
There are three general types of radioactive decay each named for exactly what is
released from the nucleus as it decays.
1. Alpha Radiation (α)
Alpha Radiation is the releasing of an alpha particle from a particle’s nucleus. An α
particle contains 2 protons and two neutrons
As an example let us take uranium. By far the most found naturally obtained form of
uranium is the isotope uranium-238.
U-238 spontaneously decays into thorium-234, in a process that emits an alpha particle.
This is called alpha decay and the atom that it emits is basically a helium nucleus.
alpha particles have relatively lower energy, they are pretty heavy as atoms go. alpha
particles can be stopped by nothing more than a sheet of paper or cloth.
2. Beta Radiation (β)
The second type of radioactive decay is beta decay, which simply emits electrons from
an atomic nucleus, transforming the original nuclide to an isobar.
Beta decay of a neutron transforms it into a proton by the emission of an electron . It has
a higher energy than alpha radiation. The thorium-234 that formed when uranium
underwent alpha decay can continue to decay on its own, and when it does, it
undergoes beta decay. Releasing an electron and an atom of xenon.
.
3. Gamma Radiation (γ)
The third type of decay is a little different, because it only emits energy, not a particle.
It's called gamma decay, and it releases electromagnetic radiation similar to visible light,
or UV radiation, but higher on the energy scale. Because it's just energy, gamma
radiation has no mass and contains no protons, neutrons, or electrons. This form of
radiation is often released when electrons transition from an unstable excited state, to a
more stable state that has a lower energy. That's called the ground state. Depending on
how much energy the electron loses, the extra energy can be released in the form of
visible, or ultraviolet light, x-rays, or gamma waves.
Take the example of nickel-60. Assume there's an atom of nickel-60 with one or more of
its electrons in an excited state. Atoms can get to this state when they are themselves
the products of radioactive decay, or if they get bombarded with radiation from other
reactions pushing their electrons into a higher energy level. Now when all those
electrons drop down to the ground state, that atom is going to release some gamma
radiation. This kind of transition can also take place where other kinds of nuclear
reactions are going on.
Half Life
Half life is basically the time it takes for exactly one half of the sample to decay. Half
lives vary with different nuclei. We can calculate how much of a sample will be
subjected to decay by knowing the half life of that sample.
When there is a more stable state, a higher energy nucleus undergoes radioactive
decay to attain it. This difference in energy is released as what's called ionizing
radiation. It's termed “ionising” because it has sufficient energy to add or remove
electrons from other atoms, essentially creating ions.
As shown, the reaction proceeds in halves, with half of whatever is left of the radioactive
element decaying every half-life period.
The amount of radioactive isotope remaining after a given number of half-lives can be
calculated using the following formula :
The decay reaction and T½ of a substance are specific to the isotope of the element
undergoing radioactive decay.
STIMULATED NUCLEAR REACTIONS
Although elements undergo radioactive decay naturally, nuclear reactions can also be
stimulated artificially. Although these reactions also occur naturally, we are most familiar
with them as stimulated reactions. There are two such types of nuclear reactions:
1. NUCLEAR FISSION
The reaction in which a large nucleus splits into two lighter ones and releases a large
amount of energy as a side product is termed as fission. The products of the reaction
are more stable than the reactants and this is what drives the reaction.
A nuclear fission reaction is almost always triggered by “firing” a neutron at an element
which splits it into two(or more) lighter elements, during which the bond energy of the
parent atom is released mainly as the kinetic energy of the escaping particles which is
transmitted to the surrounding as heat.
The Fission Reaction of Uranium-235
During the fission of uranium-235, two daughter products and three free neutrons are
released. These free neutrons can stimulate the fission of a nearby uranium-235 atom
if it collides with it and can start a self-sustaining nuclear chain reaction
This chain reaction is the principle of nuclear power. More and more atoms continue to
split, releasing a significant amount of energy which can be harvested and used to
produce electricity.
2. NUCLEAR FUSION
Fusion reactions are very different from fission, it's pretty much the opposite. For one
thing, the energy released in a fusion reaction dwarfs the energy output of fission
reactions. A common example we see everyday is the work done by our sun. The
reactions that drive our sun are like most fission reactions, in which two light nuclei join
together to form a heavier one. Hydrogen molecules are fused into helium and heavier
elements inside of stars. A lot of energy is released during this in the form of heat and
gamma radiations.
CONCLUSION
This report hopes to provide holistic development in nuclear chemistry for its readers as
it did for me. In addition to that, it also educates about its types and consequences of the
precarious reaction. Finally it also ultimately serves as a hope for future generations to
solve problems never fathomed to exist and strives to make minds wander to the
possibilities of its applications after understanding the basic principles and mechanism
behind the phenomenon.
BIBLIOGRAPHY
1. https://www.encyclopedia.com/science/news-wires-white-papers-andbooks/nuclear-chemistry
2. https://en.m.wikipedia.org/wiki/Primordial_nuclide
3. https://www.visionlearning.com/en/library/Chemistry/1/NuclearChemistry/59
4. https://www.scribd.com/document/295222026/EOCQ-ans-16
5. https://www.youtube.com/watch?v=I0IgOfsyrRA
6. https://www.nr8.com/narratives/5f1fb03a3c038dd8607aea4c