Nuclear Fusion Reactions
and the formation of 'heavier elements'
Know and understand that nuclear fusion is the joining together of atomic nuclei and is the process by
which energy is released in stars.
Compare the uses of nuclear fusion and nuclear fission,
but limited to the generation of electricity
and comparison of methods of generating electricity
Energy resources & uses, general survey & trends, comparing sources of renewables, non-renewables
At the extremely high
temperatures (107 oC = 10 million degrees!) in the 'heart' of stars the atomic nuclei have such enormous speeds
and kinetic energies that on collision they can fuse together - the nuclear
process of fusion.
Extremely high temperatures (and
needed to give the particles sufficiently high kinetic energy to overcome the natural and massive
forces of the two positive
nuclei involved e.g. two positive hydrogen nuclei (+) <==> (+).
The process by
which a heavier atomic nucleus is made from two smaller atomic nuclei is called
and these changes also release enormous amounts of energy.
In a nuclear fusion process two smaller
atomic nuclei may fuse into one larger nucleus or a larger nucleus that
either of the starting nuclei plus a smaller nucleus.
Either way a heavier nucleus is created.
One advantage of nuclear fusion over
nuclear fission is that little radioactive
waste is produced, BUT, technically, nuclear fusion has proved
technically very difficult to produce a continuous energy output, and we are
a very long way from a nuclear fusion power station generating electricity.
The lightest atom is hydrogen, this is converted to helium and gradually all the
other elements up to uranium must have been formed in stars like the Sun, but it
takes a massive star undergoing a supernova explosion to make the heaviest
Attempts are being made by
nuclear scientists and engineers to build prototype nuclear fusion reactors
BUT the task of maintaining nuclear fusion is proving extremely difficult.
You have to maintain an extremely high temperature and confine and control
the plasma of hydrogen atoms fusing into helium atoms with powerful magnetic
fields and this is proving technically very difficult, since you can't use a
So far, in a few experimental fusion
reactors, fusion has only been created for a
fraction of a second but cannot be controlled and sustained yet!
In fact its taking far more power to
create the fusion than any energy released, not a good deal for the consumer
at the moment!
Examples of fusion nuclear equations
(get the balancing?) ....
===> hydogen-2 + positron (beta plus particle)
(initially a heavier isotope of hydrogen is formed and a positron)
+ hydrogen-2 ===> helium-3
two hydrogen-2 ===> hydrogen-3 + hydrogen-1
two hydrogen-2 ===>
helium-3 + neutron
===> helium-3 + neutron
===> helium-4 + two hydrogen-1
hydrogen-2 ===> helium-4 + neutron
helium nuclei fuse to form lithium,
then from carbon to oxygen etc.
and lots of alternative fusions like
(k) gradually building up elements with increasing atomic and mass numbers, and
finally the massive isotope of uranium,
the biggest 'naturally' occurring
(a), (b) and
are believed to be the main initial energy releasing fusion nuclear reactions in the Sun,
they happen quite nicely at 15 000 000oC!
main sequence stars, like our own sun, converting hydrogen to helium in nuclear fusion,
and also in red giants the elements from lithium (3Li) to iron (26Fe)
are formed from fusing heavier nuclei, BUT ...
On 'Earth' super-heavy' elements
are being made in nuclear reactors by bombarding elements like uranium (atomic
number 92) with lighter particles
Elements heavier than
iron, (cobalt to uranium, atomic numbers 27 to 92), are only formed in a supernova
explosion of a red supergiant in a truly 'cosmic' scale explosion, where the temperatures are much higher
than the 15 million degrees of the Sun!
The positive nuclei of heavier
elements need enormous kinetic energies to overcome the massive repulsion
forces between the positively charged nuclei, and fuse to make an
even larger nucleus.
The hydrogen atomic bomb - the
ultimate nuclear weapon uses fusion, not fission
The hydrogen atomic bomb was developed
after WW2 in which fission bombs were dropped on the Japanese cities of
Hiroshima and Nagasaki.
As already mentioned, an extremely high
temperature is needed.
This is provided uses the energy from
uncontrolled nuclear fission to produce the necessary temperature for
So, the hydrogen bomb is triggered to
reproduce the energy releasing nuclear physics of a sun.
The hydrogen fusion bomb is many times
more powerful than a fission bomb.
APPENDIX 'COLD FUSION'
Cold fusion is
nuclear fusion at low temperatures e.g. room temperature (NOT millions of
In 1989 two scientists called Stanley Pons
and Martin Fleischmann reported in scientific research paper that using a simple
electrolysis cell system they had caused hydrogen atoms to fuse at room
They reported that much more heat energy was
evolved compared to the electrical energy passed into the cell.
However their paper had NOT been peer
reviewed, that is, read and their work validated by other independent
Many scientists were sceptical about their
work, and since 1989, few scientists, if any?, have reliably reproduced their
Therefore, the scientific community does not
officially accept that cold fusion is possible at the moment.
This is how science works, results must be
reproducible in laboratories all around the world and so cold fusion theory is
not accepted as a viable scientific concept.
The production of Trans-Uranium Elements
- very heavy elements!
Heavy atomic nuclei tend
to be naturally unstable and for example, many long lived isotopes of uranium
(U92) finally decay via a series of relatively short-lived radioisotopes to
produce stable isotopes of lead (82Pb).
No element higher than
uranium (92U) is found in nature except for traces of neptunium (93Np)
and plutonium (94Pu) isotopes. These are found in uranium ores
but are produced by neutron-uranium collisions rather than from the Earth's
origin. The neutrons come
from the spontaneous fission of the unstable
uranium isotope 235U and
gives rise to heavy element 'synthesis' sequence e.g.
Even heavier or
'trans-uranium' elements can be made by
bombarding a heavy atomic nucleus with a smaller ionised atom particle, in an ion
However many of the
heaviest are only produced in minute quantities as little as a few
hundred atoms in accelerator collisions.
In an accelerator the two
atoms are ionised and accelerated in powerful electromagnetic fields to very high speeds eg close to speed
of light, but in opposite directions and are then allowed to collide. The high kinetic
energies are needed to overcome the repulsion of the two positive
See examples 1. to 3. below.
The heavier elements are also
made by neutron bombardment in a nuclear reactor.
So, from these two methods, a
whole series of man-made or 'artificial' elements from atomic number
93 to 112 have been synthesised.
Where they are formed in nuclear
reactors from neutron collision (e.g. plutonium), they can be chemically separated in quantities ranging
from micrograms to kg in order study their physical and chemical properties.
Note again, the balancing of nuclear equations e.g.
uranium-238 + nitrogen-14
===> einsteinium-248 + four neutrons
formation of einsteinium from uranium and nitrogen nuclei
uranium-238 + carbon-12
===> californium-246 + four neutrons
formation of californium from uranium and carbon
californium-252 + boron-11
===> lawrencium-257 + six neutrons
formation of lawrencium from californium and boron nuclei
plutonium-239 + two neutrons
===> americium-241 + beta minus particle
formation of americium from plutonium and neutrons
and NUCLEAR PHYSICS NOTES INDEX
types, properties, uses and dangers
Level (~US grade 8-10) School Physics Notes
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Level (~US grade 8-10) School Chemistry Notes
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structure, radioactivity and
nuclear physics revision notes index
Atomic structure, history, definitions,
examples and explanations including isotopes
structure and fundamental particle knowledge needed to understand radioactivity
is Radioactivity? Why does it happen? Three types of atomic-nuclear-ionising radiation
3. Detection of
radioactivity, its measurement
and radiation dose units,
- radioactive materials, background radiation
4. Alpha, beta & gamma radiation - properties of 3 types of radioactive
nuclear emission & symbols
,dangers of radioactive emissions - health and safety issues and ionising radiation
Uses of radioactive isotopes emitting alpha, beta (+/–) or gamma radiation in
industry and medicine
6. The half-life of a radioisotope - how
long does material remain radioactive? implications!, uses of decay data and half-life values
archaeological radiocarbon dating, dating ancient rocks
actually happens to the nucleus in alpha and beta radioactive decay and why? nuclear
production of radioisotopes - artificial sources of radioactive-isotopes,
fusion reactions and the formation of 'heavy elements' by bombardment techniques
Nuclear Fission Reactions, nuclear power
as an energy resource
multiple choice QUIZZES and WORKSHEETS
Tier Radioactivity multiple choice QUIZ
Tier Radioactivity multiple choice QUIZ
Worksheet QUIZ Question 1 on
RADIOACTIVITY - absorption of alpha, beta and gamma radiation
Worksheet QUIZ Question 2 on
RADIOACTIVITY - dangers & monitoring ionising radiation levels
Worksheet QUIZ Question 3 on
RADIOACTIVITY - revision of atomic structure
QUIZ Question 4 on RADIOACTIVITY -
what happens to atoms in radioactive decay?
Worksheet QUIZ Question 5 on
RADIOACTIVITY - uses of radioisotope and half-life data
ANSWERS to the WORD-FILL WORKSHEET QUIZZES
puzzle on radioactivity
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