Download Nuclear Radiation and Decay File

Bell Ringer:
Define using the
graphic organizer:
Radioactivity
alpha particle
beta particle
gamma ray
half-life
fission
fusion
tracer
alpha decay
beta decay
cloud chamber
bubble
chamber
Geiger counter
background
radiation.
Nuclear Radiation
Radioactivity
The Strong Force
• How do you suppose protons and neutrons
are held together so lightly in the nucleus?
• Another force, called the strong force,
causes protons and neutrons to be attracted
to each other.
Radioactivity
The Discovery of Radioactivity
• In 1896, Henri Becquerel left uranium salt in
a desk drawer with a photographic plate.
• Later, when he developed the plate, he found
an outline of the clumps of the uranium salt.
• He hypothesized that the uranium salt had
emitted some unknown invisible rays, or
radiation, that had darkened the film.
Radioactivity
The Discovery of Radioactivity
• Two years after Becquerel’s discovery, Marie
and Pierre Curie discovered two new
elements, polonium and radium, that also
were radioactive.
• After more than three years, they were able to
obtain about 0.1 g of radium from several tons
of pitchblende (uranium oxide minerals).
Radioactivity
• The process by which an unstable
nucleus emits one or more particles
of energy.
• The released energy or particles are
called nuclear radiation.
Nuclear Decay
• Produces nuclear radiation as a by
product.
• Process by which an element can
transform into a different isotopes of
the same element or change into an
entirely new element.
Types of Nuclear
Radiation
• Alpha and beta
radiation are
particles.
Gamma
radiation is an
electromagneti
c wave.
Alpha Particles
• Positive Charged
Particle
• Made up of 2 protons
and 2 neutrons.
• Has the same mass as a
helium atom.
• Emitted by some
radioactive nuclei.
• Ionizes material as it
passes through it.
• Most massive type of radiation.
• Does not travel far through a substance.
Nuclear Decay
Alpha Particles
• Notice that the
alpha particle and
its symbol is the
same as a helium
nucleus,
.
• An alpha particle
has an electric
charge of +2 and
an atomic mass
of 4.
Nuclear Decay
Smoke Detectors
• Some smoke detectors give off alpha particles
that ionize the surrounding air.
Nuclear Decay
Smoke Detectors
• If smoke particles enter the ionized air, they
will absorb the ions and electrons. The circuit
is broken and the alarm goes off.
Beta Particles
• Negative Charged Particle
• Emitted during the
radioactive decay of
neutrons.
• Neutron decays into a proton
and an electron.
• The proton stays in the
nucleus.
• The electron is emitted.
• Ionize material as it passes
through.
Beta Particles
• Because the atom now has one more proton, it
becomes the element with an atomic number
one greater than that of the original element.
• However, because the total number of protons
and neutrons does not change during beta
decay, the mass number of the new element is
the same as that of the original element.
• Travels farther through a material
than alpha radiation.
Nuclear Decay
Gamma Rays
• They have no mass
and no charge and
travel at the speed
of light.
• The properties of
gamma rays are
summarized in the
table.
Gamma Rays
•
•
•
•
•
High energy electromagnetic radiation.
Are not made of matter.
No electric charge.
Does not ionize material.
However, gamma rays cause more damage
to biological molecules as they pass through
living tissue.
• Can travel far through a material.
• Concrete has to be 2 meters thick to
stop gamma rays.
Alpha Decay
• In alpha decay, two protons and two
neutrons are lost from the nucleus.
Nuclear Decay
18.2
Alpha Decay
• The new element has an atomic number two
less than that of the original element.
• The mass number of the new element is four
less than the original element.
• In this decay,
polonium emits
an alpha particle
and changes into
lead.
Nuclear Decay
18.2
Beta Particles
• Nuclei that emit beta particles undergo Beta
Decay.
Nuclear Decay
18.2
Beta Decay
• The new element has an
atomic mass that is the
same as the original
element.
• Because the atom now has one more proton, it
becomes the element with an atomic number
one greater than that of the original element.
• However, because the total number of protons
and neutrons does not change during beta
decay, the mass number of the new element is
the same as that of the original element.
Nuclear Decay
18.2
Beta Decay
• Nucleus gains a proton and loses a neutron
-Ex. Iodine will decay to Xenon by emitting a
beta particle.