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Science 11th grade
LEARNING OBJECT
LEARNING UNIT
Why does the sun release so much energy?
How do world components
change?
S/K
Skill 1: Explain atomic models developed through
history based on experimental evidence.
Skill 2: Explain radioactive decay phenomena α and β
based on the current atomic model.
Skill 3: Explain how nuclear energy is obtained from
atom structure alteration, and contrast its risks and
benefits.
Skill 4: Explain the principles, which have led to use
of radioisotopes in medicine.
Skill 5: Argument why carbon 14 measure allows us
to determine the age in fossils.
Skill 6: Talk to a partner about why the discovery of
atomic models was important for humanity.
Language
English
Socio cultural context of
the LO
Colombia
Curricular axis
Physical Environment
Standard competencies
Establish relations between gravitational and
electrostatic fields, as well as, electric and magnetic
fields.
Background Knowledge
Gravitational force, electrical force, mass-energy
relation, periodic table.
English Review topic
Past Simple
Vocabulary box
•
•
Leaf: (n) something thin like a leaf, especially the
page of a book.
Bounce: (V) to hit a surface and then move
quickly away, or to make something do this.
•
•
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Crust: (n) a hard surface especially the outer
layer of the earth.
Feasible: (adj.) possible to do.
Mold: (n) a green or black substance that grows
in wet places or on old food.
Beam: (n) a line of light that shines from
something.
NAME: _________________________________________________
GRADE: ________________________________________________
Introduction
They discovered an important and unique paleontological piece in
Colombia: A seven-meter long Kronosaurus. This is kept at the fossil
museum in Villa de Leyva as part of an invaluable fossil collection.
This marine reptile, which lived a little more than 100 million years ago,
is the most complete found so far.
Have you asked yourself what archeologists have done to determine the
age of this and other fossils found?
You will be able to answer that question as you progress in this learning
unit.
In addition, you will find key information, which will help you better
understand radioactive processes existing in nature, and how human
beings have been able to use those for our benefit.
Objectives
1. To explain some nuclear reactions and interpret its disintegration
kinetics.
2 To argue about radioactivity advantages and disadvantages.
3. To assume a critical position in relation to electrical power generation
through nuclear processes.
Activity 1
Skill 1: Explain atomic models developed through history based on
experimental evidence.
Skill 2: Explain radioactive decay phenomena α and β based on the
current atomic model.
Atomic Models
Dalton’s atomic model. He raised the following postulates:
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•
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Atoms are indivisible and indestructible.
Atoms belonging to one same element are all equal but different
to the ones belonging to another element.
Atoms in one element can combine with atoms belonging to
another element, forming new atoms.
Thomson’s atomic model: He discovered the electron in an
experiment with gases trapped in a vacuum tube. When he applied
several thousand volts to them, they emitted colored light beams called
cathode rays, which are deviated by electric and magnetic fields.
After carefully studying the deviation presented by cathodic rays,
Thomson proved the existence of negatively-charged particles he called
electrons and he stated:
•
Atoms are spherical and have a positive charge distributed evenly
around its entire volume. On the other hand, electrons are negative
charge particles embedded all over the sphere. (Fig.1).
Figure 1. Thomson’s Atomic Model
Negative charge particles embedded in a positive sphere.
Retrieved from:
http://4.bp.blogspot.com/_EoFgsPmlS1g/TOcm3hrbt_I/AAAAA
AAAAAs/JcESHUG-Zok/s1600/image_gallery.jpg
Very important…
Electrons are assumed as electrical or elemental charge units, since a
lower charged particle has not been discovered. Its value is -1.6·1019
Coulombs.
Rutherford’s Atomic Model: He stated an atom made of a central
nucleus and a crust (Fig. 2).
Figure 2. Rutherford’s Atomic Model
Nucleus and crust structured
Retrieved from:
https://edbar01.files.wordpress.com/2014/05/atom.gif
Rutherford was able to prove the existence of a nucleus, due to an
experiment in which he managed to make an alpha beam influence a
gold leaf projected on a fluorescent screen. There they observed how
the majority of the particles followed the same direction, but some of
them were deviated and others, in less quantity, bounced towards the
sender (Fig. 3).
Figure 3. Rutherford’s experiment.
Alpha particles influencing a gold leaf.
Retrieved from:
http://concurso.cnice.mec.es/cnice2005/93_iniciacion_interacti
va_materia/curso/materiales/atomo/bombardeo.htm
With this experiment, Rutherford was able to state that:
•
•
The nucleus had a very small size compared to the total atom size.
This is where the positive charge and approximately the entire
atom mass concentrated.
The entire negative charge was at the crust; such charge was
represented by electrons.
Bohr’s Atomic Model: He proposed the atom crust was structured at
different energy levels where the electrons were located. If an electron
absorbs energy from the outside, it could move up from a level E1 to a
higher energy level E2 and there it would last a very short time, to
finally return to its original level E1 emitting light (Fig. 4).
Figure 4. Bohr’s atomic model.
An electron can move up from one energy level to another one.
Retrieved from:
http://www.emdialogo.uff.br/sites/default/files/images/saltoq
uantico.jpg
In such a way, electrons turn around the nucleus in orbits featuring
concrete energy values, therefore, not every orbit is allowed but a finite
number.
Did you know that…?
Visible White light coming from the sun can decompose in different
colors using a prism, obtaining a continuous spectrum.
Atom Current Model
In the same way as Einstein proposed wave-particle duality regarding
light behavior, De Broglie raised the possibility that electrons and other
particles can also have wave properties.
According to this possibility, and after proving electron diffraction,
Schrödinger proposes a new Atom Model stating that:
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•
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Every moving electron is associated with a wave.
The concept of probability is introduced to describe position,
speed and electron energy at a specific time frame.
Electron energy is quantized, it means, it can only have certain
values.
Schrödinger’s wave equation establishes the region of space where it is
more feasible to find an electron. This region is called orbital and has a
shape and size determined by the energy of the electron. (Fig. 5).
Figure 5. Current Atomic Model.
Regions where it is more feasible to find the electron.
Retrieved from:
http://clasedelaquimica.weebly.com/uploads/1/9/2/6/192625
71/105713766.jpg
Very important…
Heisenberg’s uncertainty principle states that it is not possible to know
the position and speed of an electron simultaneously and with absolute
accuracy.
Atomic Nucleus
The nucleus in atoms is composed of protons and neutrons, which remain
linked by a strong nuclear force. (Fig. 6).
Figure 6. Atomic nucleus.
Positive protons and neutrons with no electrical charge.
Retrieved from http://www.nodo50.org/cerraralmaraz/Image9.jpg
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Protons have positive charge with same value as the charge of
electrons, but their mass is 1,840 times higher.
Neutrons do not have charge and their mass is a bit higher than
the mass of protons.
Some atomic nuclei have a proton and neutron combination, which
does not respond to a stable configuration, those unstable nuclei are
radioactive.
Radioactivity
It is the phenomenon originated because of the spontaneous
disintegration of some heavy atomic nuclei, and high-energy
electromagnetic radiations or emission particles are emitted. The
particles which can be released in a radioactive disintegration are: (see
figure 7):
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•
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Alpha (α): It is made of a helium atomic nucleus, which has two
protons and two neutrons. They are scarcely penetrating particles
and a piece of paper can stop them.
Beta (β): They are electrons emitted to high speeds close to the
speed of light. They are more penetrating particles than the alpha
ones and can be stopped by a metal sheet.
Gamma (γ): They are highly energetic particles with no mass.
They are highly penetrating particles and are stopped by a lead or
concrete (cement) wall.
Figure 7. Nuclear Radiations.
Alpha (α), beta (β) and gamma (γ) penetrating particles.
Retrieved from:
http://www.100ciaquimica.net/images/temas/tema3/ima/radi
acionb.gif
Did you know that…?
Protons and Neutrons are not fundamental particles, but they are made
of smaller particles called quarks.
Alpha disintegration. When the nucleus releases an alpha particle, it
transforms into a new element. The uranium most common isotope is U238, which contains 92 protons and 146 neutrons. When uranium
disintegrates, it releases an alpha particle, having Thorium Th-234 as a
result, which contains 90 protons and 144 neutrons.
Another example is americium Am-241 disintegration, which results in
Neptunium Np-237 when releasing an alpha particle. (Fig. 8).
Figure 8. Alpha disintegration.
Americium-241 disintegration into Neptunium-237, releasing an
alpha particle.
Beta disintegration. When the nucleus releases a beta particle, it
transforms into a new element. Thorium Th-234 is also radioactive and
at the moment of disintegrating, it releases a beta particle from its
nucleus. This is possible since an electron becomes a proton and a
neutron, but the proton remains in the nucleus, so the number of
protons at the nucleus increases by one, having Protactinium as a new
element Pa-234 with 91 protons and 143 neutrons.
Another example is Hydrogen H-3 (Tritium), which becomes Helium He3 since it emits a beta particle from its nucleus. (Fig. 9).
Figure 9. Beta disintegration.
Retrieved from:
http://web.educastur.princast.es/proyectos/jimena/pj_francisc
ga/leydesin.htm
Radioactivity Kinetics. The number of atoms, which disintegrate at a
given time, is directly proportional to the number of atoms present in
the sample. Constant proportionality is known as disintegration
constant.
Radioactive Disintegration Simulator.
Remember that…
An isotope is an atom belonging to the same chemical element; it has the
same proton quantity, but a different number of neutrons.
Learning Activity 1
The following activity will help you strengthen concepts about the
Atomic Models, which have been developed through history.
Match the following experimental evidences to its corresponding Atomic
Model:
Evidence
Model
1. When applying a high voltage to the atoms of an
element in gaseous state, these emit particles with
negative charge.
A. Dalton’s
atomic
theory.
2. Electron leaps from higher to lower energy levels or
vice versa involve either emission or absorption of
electromagnetic energy. (Light photons).
B. Thomson’
s atomic
theory.
3. The crust is practically an empty immense space
compared to the dimensions in the nucleus.
C. Rutherfor
d’s
atomic
theory.
4. Electrons occupy a region of space according to a
probability distribution.
D. Bohr’s
atomic
theory.
5. In chemical reactions, atoms exchange themselves
from one substance to another, but no atom
belonging to an element disappears or transforms
into the atom of another element.
E. Current
Atomic
Model.
Activity 2
Skill 3: Explain how nuclear energy is obtained from atom structure
alteration, and contrast its risks and benefits.
Skill 4: Explain the principles, which have led to use of radioisotopes in
medicine.
Nuclear Fusion
Nuclear strength is responsible for keeping protons and neutrons
together in the center of the atom. In uranium and other heavy
elements, nuclear force is not so strong. Consequently, electric repulsion
forces between protons can defeat nuclear force and divide the nucleus
into two; this phenomenon is called Nuclear Fusion.
Figure 10. Fission Reaction.
Uranium-235 fission chain reaction, divided into Barium-141 and
Krypton-92.
Retrieved from: https://quimica-iti-1213.wikispaces.com/file/view/17_2.jpg/385552358/17_2.jpg
In figure 10, we can see a neutron impacting a nucleus of Uranium U-235
neutron, which is divided into two lighter atoms (Barium Ba-141 and
Krypton Kr-92), releasing energy and three neutrons, which will affect the
other Uranium nuclei generating a chain reaction eventually.
In Colombia, the “Servicio Geológico Nacional” started to carry out
geological studies in 2010 to explore Uranium, Thorium and Potassium in
potential areas located in Boyacá, Cundinamarca and the southern region
of the province called Santander. They found Uranium in all the studies.
Did you know that…?
Only 0.7% of Uranium found in a natural way corresponds to isotope U235 used in nuclear reactors.
Nuclear Fusion
Another way to generate nuclear energy is by means of a union of two
light atomic nucleuses to form a heavier one. This process is called
Nuclear Fusion and can generate more energy by fusion than by fission;
this kind of energy is evidenced in the speed reached by the released
neutrons. Therefore, a great amount of heat quantity would be obtained
when those neutrons stop; this could be transformed into electrical
power.
.
Figure 11. Fusion Reaction.
Deuterium and Tritium fusion to form Helium atoms by releasing
a neutron and an amount of energy.
https://sputnik87.files.wordpress.com/2011/01/fusionnuclear-infografc3ada1.png
In figure 11, we can see the Nuclear Fusion of two hydrogen isotopes,
Deuterium H-2 and Tritium H-3, forming a helium nucleus and releasing
a neutron and a considerable amount of energy. This nuclear reaction is
the one occurring in our sun.
In Colombia, through Universidad Nacional, they want to be part of the
TEIR (Thermonuclear Experimental International Reactor) project, which
seeks to produce electrical power in order to use it commercially through
Nuclear Fusion. Universidad Nacional contributes to this project by
encouraging research groups, making students participate, collaborate
and work in professor and student exchanges.
Did you know that…?
The quantity of Deuterium H-2, which is found in a liter of water, is able
to release an amount of energy equivalent to the one found in 88 gas
gallon.
Nuclear Plant
A nuclear plant is a facility, which takes advantage of the heat obtained
from the Nuclear Fission of radioactive elements such as Uranium or
Plutonium to generate electrical power. In the following animation, you
can see the steps to obtain electrical power in a nuclear plant.
Figure 12. Nuclear Plant.
Transformation process of nuclear energy into electrical power
in a nuclear plant.
Retrieved from:
https://www.youtube.com/watch?v=nMZJ7ABkvRw
1. Double security retaining Wall (concrete and steel walls).
2. Reactor nucleus: Here you can find the fuel (Uranium or Plutonium),
which releases heat by fission.
3. Steam Generator: water tank, which evaporates because of the heat,
delivered by the reactor.
4. Turbines and generator: Turbines are moved by water steam and
generate electrical power.
5. Transformer: it transforms voltage into a suitable value for its
distribution.
6. Electricity grids: they transport electrical power.
7. Cooling tower: Water steam, which moves the turbines, goes to a
condenser, which cools it down and makes it liquid so that it can be
thrown back into lakes or rivers.
Colombian Nuclear Reactor. In Colombia, there is a small 30 kilowatt
Nuclear Reactor IAN R-1, which is used for research. It was donated by
the United States Government in 1965 and was renewed in 2009 in a
new treaty between the International Physics Center and the Servicio
Geológico Nacional, which is the institution in charge of the “Programa
Estratégico de Energía Nuclear” in Colombia as the reactor administrator
and operator.
Fifty years with the nuclear reactor in Colombia.
Radiation: uses and damages
In figure 13, you can see some of the most relevant radioactive
processes; and figure 14 shows the damages caused to human beings.
Uses
Medicine and research: X rays produce
bone images from the inside of our
organisms. Also the radioisotope techique
is used for diagnosing diseases.
Industry: Radioisotopes are employed
to determine the speed of a fluid, detect
leaks in pipelines, non-destructive
analysis of machinery pieces, among
others.
Agronomy : to detect the path followed
by sinthetized carbohydrates in
vegetables.
Science: C-14 to determine the age of
antiques, verify the authenticity of art
pieces, nuclear plants, definition of
underground water flows, etc.
Food preservation: It destroys and
disables bactera and mold spores found
in food.
Figure 13. Radiation Uses.
We can see different fields where radioactivity is exploited.
By the Author.
Figure 14. Info graphic image on radiation effects.
We can see some negative effects of radiation on the human
body.
Retrieved from http://4.bp.blogspot.com/-bUDAw2QiIc/Tarb4zKAiyI/AAAAAAAALys/pr2g61BdDms/s1600/EFECTOSDE-LA-RADIACION-EN-EL-ORGANISMO-HUMANO.jpg
Radioisotope in medicine
Radioactive isotopes are highly used in medicine to diagnose heart,
lung, renal, and brain diseases, among others. There are natural and
human-made isotopes, but for medical use, they only use the ones
produced by nuclear reactors, since they have the necessary
characteristics for its function.
Figure 15. Medical Scanner.
It is used to detect osseous diseases.
Retrieved from:
http://www.cancer.gov/images/cdr/live/CDR742469-750.jpg
Some radioisotopes emit alpha or beta radiation, which is used to treat
diseases like cancer. Others emit gamma or positron radiation, which
are used along with powerful medical scanners to take pictures of
processes and structures inside the body. (Fig.15).
The most used radioisotopes in medicine are:
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Technetium Tc-99: to study the brain, lungs, liver, arm and bones.
Chromium Cr-51: for taking images of the arm and locate internal
bleeding.
Sodium Na-24: to detect vascular injuries.
Strontium Sr-85: to make pictures of bones and check cracks or
osteoporosis.
Samarium Sm-153: used in bone cancer treatment, it acts as a
painkiller for the pain caused by metastasis.
Thallium Tl-201: Used to detect the obstruction in coronary
arteries.
Iodine I-131: used to detect the cause of thyroid dysfunction.
Very Important…
Radioisotopes administered to patients during diagnosis or treatment,
falter or are totally eliminated becoming stable (non-radioactive)
elements, within some minutes or hours.
Learning Activity 2
The following activity will help you to strengthen concepts related to
radioisotopes used in medicine.
Complete the table with the information about the most common
radioisotopes used in the field of medicine. Use the periodic table
offered to you in the following link: http://www.ptable.com/?lang=es
Radioisotope
Symbol
# Protons
# Neutrons
Samarium-153
Sm
62
91
Technetium99
Chromium-51
Sodium-24
Estrontium-85
Iodine-131
Activity 3
Skill 5: Argument why carbon 14 measure allows us to determine the age
in fossils.
Carbon C-14
A stable carbon atom has six protons and six neutrons. In Carbon 14, its
unstable (radioactive) isotope has six protons and eight neutrons (Fig.
16) and it is present in considerable amounts in the earth atmosphere.
Figure 16. Carbon Isotope.
We can see the three atoms feature the same number of protons
and neutrons, but a different neutron number.
Retrieved from http://2.bp.blogspot.com/AdgroiL0B1E/TsoDfBLNaeI/AAAAAAAAAZQ/HyfKDkbWpkI/s160
0/is%C3%B3topos+de+carbono.jpg
Cosmic radiation produces neutrons, which come into the atmosphere
and react to Nitrogen producing a heavy carbon isotope C-14. This
mixes with common carbon C-12, in atmospheric oxygen; it goes into all
living beings through Carbon dioxide. Plants absorb it during
photosynthesis, which are then eaten by herbivores, which are
carnivore’s food. When a living being dies, the carbon atom absorption
stops and its concentration by radioactive disintegration starts to
decrease.
Remember that…
An average lifetime is the time that needs to pass for half of the atoms
in a radioactive atom sample to disintegrate into atoms of lighter
elements
Carbon -14 Dating
The average life period of C-14 is 5,730 years, this means that after
5.730 years half of the original quantity of the isotope has faltered; after
a similar period, what was left is reduced to a half, which reduces it to a
quarter of the total initial and so on. Measuring the quantity of Carbon
14 in a fossil, we can determine its approximate age. The mass in
Carbon-14 belonging to any fossil decreases at an exponential rate,
which is known, as we can observe in figure 17.
Figure 17. Average C-14 life
We can see the relation between the number of particles of C-14
and time in years.
Retrieved from:
http://bibliotecadigital.ilce.edu.mx/sites/ciencia/volumen1/cie
ncia2/08/htm/sec_8.html
Example. A man’s prehistoric human remains were found in the
Nemocón valley (Fig.18). They were analyzed by using the Carbon 14
technique. The amount of Carbon-14 was determined by means of a
radioactive particle counter, and it was compared to the quantity of
Carbon-14 in the atmosphere at different eras. The result was that this
fossil was approximately eight thousand years old.
Figure 18. Checua man.
This was an archeological finding in Nemocón.
Retrieved from:
http://lapaleontologiaencolombia.blogspot.com.co/2014/05/elmastodonte-de-nemocon-cundinamarca.html
Did you know that…?
Carbon 14 method is only useful for determining fossil ages from 45,000
to 50,000 years.
Learning Activity 3
The following activity will help you better understand why Carbon 14
measurement allows us to know the age of fossils.
Answer True (T) or False (F), as appropriate.
Answer True (T) or False (F) as it corresponds:
1. Carbon 14 can determine the earth’s age. ( )
2. When 70,000 years have passed, the Carbon 14 percentage found in
a fossil is null. ( )
3. Carbon-14 is absorbed in carnivores after consuming herbivores ( )
Complete according to the graphic in figure 17.
4. An 18,190-year-old fossil has a C-14 percentage corresponding to
__________%.
5. For finding the 25% of C14 in a fossil, ___________years must have
passed.
Abstract
Homework
The following activity allows you to go deep into knowledge regarding
radioactivity applications in determining fossils age, to do this, it is
necessary for you to review and understand the concepts presented in
activity 3.
1. Check different bibliographic references to answer the following
questions:
a. What are C-14 limitations in determining fossil ages?
b. What other radioactive elements can be used to date antique
events?
c. What is the decay chain in the elements researched on the
preceding point?
Record in your notebook.
2. Once you finish checking the information, get together with two
classmates and share the information.
3. In your group, fill the following table out comparing, at least five
radioactive elements checked. Use the following table as a model:
Number
Radioactive
Element
Average life
Nuclear
watch uses
Limitations
1
2
3
4
5
4. On a poster, draw the decay chain of one of the five elements in the
table.
5. Do a presentation to your classmates using the poster you made.
Briefly explain the importance of the element you chose concerning
the dating of antique events.
Evaluation
The purpose of this evaluation is to review the concepts studied in this
LO; to do so it is necessary for you to go over each activity, understand
the proposed resources and develop the learning activities proposed.
I.
Solve the following puzzle:
Clues
1. Radioactive decay where a helium nucleus is released.
2. Radioactive element used to determine the age of fossil.
3. Nuclear process consisting of the division of a heavy nucleus.
4. Scientist who stated the atom was made of nucleus and crust.
5. Heisenberg formulated this principle based on the Current Atom
Model.
Complete the statement:
Hydrogen isotopes are _______________ along with a proton and
a _______________ and __________________ along with
________ proton and ____________neutrons.
II.
III.
Choose the radioactive elements among the following:
• Carbon-12
• Iodine-131
• Uranium-235
• Oxygen-16
• Hydrogen-3
Bibliography
•
Romero, O., & Rincón, L. (2008). Nueva Física 11. Bogotá:
Santillana.
•
Castañeda, H. (1991). Hola Física Grado 11. Medellín: Susaeta
ediciones.
Endesa educa. (2014). Centrales nucleares. Retrieved from
http://www.endesaeduca.com/Endesa_educa/recursosinteractivos/produccion-de-electricidad/x.-las-centrales-nucleares
E-ducativa. Modelo atómico de Rutherford. Retrieved from
http://educativa.catedu.es/44700165/aula/archivos/repositorio/1000/116
2/html/2_modelo_atmico_de_rutherford.html
Biblioteca digital del ILCE. (2013). Los relojes nucleares. Retrieved
from
http://bibliotecadigital.ilce.edu.mx/sites/ciencia/volumen1/ciencia
2/08/htm/sec_8.html
Gobierno de Canarias. Modelo atómico actual. Retrieved from
http://www3.gobiernodecanarias.org/medusa/lentiscal/1CDQuimica-TIC/applets/Actual/teoriamodeloactual.htm
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Educastur. (2010). Radioactividad. Retrieved from
http://web.educastur.princast.es/proyectos/jimena/pj_franciscga/l
eydesin.htm
CNICE. (2006). Datación absoluta. Retrieved from
http://concurso.cnice.mec.es/cnice2006/material082/actividades/
paleo_c14/actividad.htm#mh2
The dinosaur picture database. Kronosaururs picture. Retrieved
from http://images.dinosaurpictures.org/Kronosaurus_5054.jpg
Modelosatomicospalacios. El átomo de Thomson. Retrieved from
https://sites.google.com/site/modelosatomicospalacios/Home/eldescubrimiento-del-electron/el-atomo-de-thomson
Wordpress.com. Física cuántica. Retrieved from
https://edbar01.files.wordpress.com/2014/05/atom.gif
Emdialogo. Saltoquantico. Retrieved from
http://www.emdialogo.uff.br/sites/default/files/images/saltoquanti
co.jpg
Clase de la química. El átomo a través del tiempo. Retrieved from
http://clasedelaquimica.weebly.com/uploads/1/9/2/6/19262571/1
05713766.jpg
Innecesaria. Energéticamente ineficiente. Retrieved from
http://www.nodo50.org/cerrar-almaraz/Image9.jpg
Ciencia Química. Penetración de las radiaciones nucleares.
Retrieved from
http://www.100ciaquimica.net/images/temas/tema3/ima/radiacio
nb.gif
Quimica ITI-12-13. (2016). Reactores de Fisión Nuclear. Retrieved
from https://quimica-iti-1213.wikispaces.com/REACTORES+DE+FISI%C3%93N+NUCLEAR
FS 210 Biofísica, Universidad Nacional Autónoma de Honduras.
Efectos de la radiación sobre el cuerpo humano. Retrieved from
https://fs210secc1002.wordpress.com/el-atomo/efectos-de-laradiacion-sobre-el-cuerpo-humano/
National Cancer Institute. (2006). Retrieved from
http://www.cancer.gov/images/cdr/live/CDR742469-750.jpg
Ciencia NXT. (2015). Datación mediante el carbono 14. Retrieved
from http://www.cancer.gov/images/cdr/live/CDR742469-750.jpg
El Espectador. (2012). Colombia cuenta con un reactor nuclear
renovado. Retrieved from
http://www.elespectador.com/noticias/nacional/colombia-cuentaun-reactor-nuclear-renovado-articulo-376262
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La Paleontología en Colombia. (2014). El Mastodonte de Nemocón,
Cundinamarca. Retrieved from
http://lapaleontologiaencolombia.blogspot.com.co/2014/05/elmastodonte-de-nemocon-cundinamarca.html#uds-search-results
Glossary
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Light beam: Set of electromagnetic rays, which head only one
direction.
Fluorescence: property of some bodies that emit a light when
radiation is received.
Prism: Transparent crystal piece which decomposes light
Spectrum: Set of radiations with different frequency.
Concrete: stone mixture, concrete and sand used in constructions.
Fossil: remains of an organic death being found petrified.
Photosynthesis: process of some vegetal cells in which they
transform inorganic substances thanks to light energy.