Transcript Where Did the Elements Come From?

Where Did the Elements
Come From?
Natural Elements
• There are 93 naturally occurring elements
• All are found on Earth except for Technetium,
Promethium, and Neptunium which have been
detected in the spectra of stars.
• Most atoms in living things come from six
elements: carbon, hydrogen, oxygen, nitrogen,
phosphorus, and sulfur
• It is believed all 93 elements were created in the
centers of stars billions of years ago.
Big Bang Theory
• An explosion of unbelievable violence,
before which all matter in the universe
could fit on a pinhead.
• Most scientists accept this model for the
universe’s beginning
• When the universe had expanded and
cooled enough the electrons, protons, and
neutrons that were formed came together
to form hydrogen and helium atoms
Formation of Stars
• Huge hydrogen clouds were pulled closer and
closer by gravity.
• As the clouds became more dense the
temperature and pressure at the center of the
clouds increased and stars were born.
• Nuclear reactions took place in the center of the
stars these reactions are the same as those that
take place in stars today
• Fusion of hydrogen nuclei into helium atoms is
one of the simplest nuclear reactions
Nuclear Fusion
• 4 Hydrogen nuclei containing 1 proton each
combine to form a Helium atom which is
composed of 2 protons and 2 neutrons.
• The mass of the hydrogen nuclei is greater than
the mass of the helium nucleus, but the mass is
not lost rather it is converted to energy, ie.
Einstein’s law of relativity E=mc2 where E is
energy, m is the mass being “lost” and c is the
speed of light.
• The energy produced by nuclear fusion is so
great it keeps the center of stars at a very high
temperature.
Other Atoms Formed by Fusion
• Because of the high temperatures in stars
the helium nuclei fuse to form a berylium
nucleus.
• A helium nucleus and a berylium nucleus
fuse to form a carbon nucleus.
• Repeated fusion reactions form elements
as massive as iron
Production of elements heavier
than iron
• When very massive stars have converted
almost all of the hydrogen and helium in its
core into heavier elements up to iron, the
star collapses, and then blows apart
producing the elements heavier than iron.
• This explosion is called a supernova.
• The contents of the star become part of a
newly forming star system.
Transmutation
• Transmutations are nuclear changes that
change one atom into another.
• This cannot be accomplished in ordinary
chemical reactions.
• The first transmutation to be documented
was that of nitrogen becoming oxygen
when struck by an alpha particle and
adding a proton to the nitrogen atom.
Synthetic Elements
• Synthetic or man made elements are
produced by a particle accelerator.
• Transuranium elements those with more
than 92 protons are synthetic
• Cyclotron produces energy pulses one
after another causing charged particles to
accelerate faster and faster until particles
collide and fuse to form atomic nuclei with
higher atomic numbers
Particle accelerators cont.
• When particles reach 1/10th the speed of
light it gains enough energy that it also
gains mass according to E= mc2.
• As the particle becomes more massive it
slows down and misses the next energy
impulse to accelerate it.
• The cyclotron can only be used to create
atoms with atomic numbers up to 106
Synchrotron
• The synchrotron is used to make superheavy
elements, elements with atomic numbers greater
than 106
• The energy pulses are timed to match the
acceleration of the particles so they will continue
to accelerate.
• Particle accelerators are very large the one in
Batavia, IL is 4 miles in circumference.
• Particles are accelerated through the accelerator
to 99.9999% the speed of light.
Life of a Superheavy Element
• Only a few nuclei are produced by a
synchrotron and they last for only a
fraction of a second.
• There is controversy over whether some
elements have actually been created by
using particle accelerators