Transcript PowerPoint Radioactivity

RADIOACTIVITY
Marie Curie
•Born in 1867 in Warsaw,
Poland
•Graduated high school
when she was 15
• In 1893 she started working
at the Sorbonne University in
Paris
Pierre
• She married Pierre Curie in July 1895
Work with Uranium
• Discovered that some materials
appeared to give off “rays” or “energy”,
even when left on their own.
Uranium Continued
•Marie discovered that
there was something
going on inside the atom
that created this effect,
and she named the effect
“radioactivity”
Radioactivity
•At the time, the
only known
elements that were
radioactive were
uranium and
thorium
Polonium Cont.
•In July 1898, Marie
discovered a new element
that was even more
radioactive than uranium
•They called this new
substance polonium in
honor of Marie’s
homeland
Radium
•In January of 1899,
she discovered
another new element
that was over 1
million times more
radioactive than
uranium, and named it
radium
World War II
•When the War broke
out, Marie donated
all of her money to
the War fund, and
signed up to be a
nurse
The first X-ray machine
•Marie had a brilliant
idea: that by using the
radiation emitted from
radium, doctors could
actually see into patients
tissues to look at their
bone structure.
X-ray machines
•Marie created 20 mobile x-ray machines and
over 200 stationary machines, that were used
widely during the war
Health Problems
•Marie believed that
working with
radium was not a
danger to her health,
however, doctors
today have proven
that she was very
wrong
Declining Health
•Marie had
been
working with
radium for
almost 12
years
•She began to
notice burns
on her hands
somewhere
around 1932
Late Life cont.
•Marie eventually contracted
leukemia and died on July 14, 1934
Awards
•Marie was awarded
the Nobel prize in
physics in 1903 for her
work with X-rays
•She was also awarded
the Nobel prize in
chemistry in 1911 for
her work with radium
Radioactivity: what is it?
In some types of isotopes, the nucleus is unstable, and will
decay into a more stable atom.
This decay is completely spontaneous.
Radioactivity: what is it?
The breaking up of the nucleus of an isotope
(form of an element) is called radioactivity.
As a result of this break-up, particles or energy
is emitted.
Remember: What are isotopes?
These atoms are isotopes of hydrogen. They all
have one proton and one electron, but different
numbers of neutrons.
The many types of radiation
May the Force Be With you
• Inside the nucleus there are two completely different
forces acting.
1) An electric force of repulsion between the protons.
On its own this would blow the nucleus apart
2)The nuclear force, a strong force of attraction
between nucleons, which acts only over a very short
range.
• In a stable nucleus there is a delicate balance
between the repulsive electrical forces and the
attractive nuclear force.
• For small nuclei the up to about 20 the ratio of P to
N is about 1 but as nucleus becomes bigger so does
the ratio of N to P.
• Eg Bismuth 209 heaviest stable isotope, has 83 p
and 126 n and is stable.
• Bi 211 is unstable and ejects and alpha particle in an
attempt to attain nuclear stability.
• Higher than Bi83 simply have too much repulsive
charge and additional neutrons are unable to
stabilize their nuclei. All of these atoms are
radioactive.
•
Alpha particles consist of two protons and two
neutrons, identical to the nucleus of a helium
atom.
• A sheet of paper or a person’s surface layer of
skin will stop them.
• Alpha particles are only considered hazardous to
a person’s health if they are ingested or inhaled
and thus come into contact with sensitive cells
such as in the lungs, liver and bones.
•
Beta particles are electrons emitted from the nuclei
•They can travel a few
feet in air but can usually
be stopped by clothing or
a few centimeters of
wood.
•They are considered
hazardous mainly if
ingested or inhaled, but
can cause radiation
damage to the skin if the
exposure is large enough.
•.
An unstable neutron
decays into a proton and
an electron
• Gamma rays are a form of electromagnetic
radiation (like light, radio, and television) that
come from the nucleus of a radioactive atom.
– Occurs when an unstable nucleus emits electromagnetic
radiation. The radiation has no mass, and so its emission
does not change the element.
– They penetrate matter easily and are best stopped by
water or thick layers of lead or concrete.
– Gamma radiation is hazardous to people inside and outside
of the body.
Video + Worksheet
Alpha Emission
Occurs when the nucleus has
too many protons & neutrons
which causes instability. 2
protons & 2 neutrons
emitted.
238
92
parent
nuclide
U
Th  He
234
90
daughter
nuclide
4
2
alpha
particle
Numbers must balance!!
Alpha Emission
Ex. Plutonium-239 undergoes alpha decay
239
94
Atomic Mass:
Atomic #:
235
92
Pu
239
94
U
=
235
=
92
+
+
+
4
2
He
4
2
Masses must be equal = Conservation of mass
Alpha Emission- Challenge!
Ex. Polonium-210 undergoes alpha decay to produce
this daughter nuclide. What is the daughter nuclide?
210
84
Atomic Mass:
Po
210
-
210
Atomic #:
A
Z
4
=
=
2
=
=
84
84
A
Z
-
X
=
+
A
A
+
X
=
206
Z
+
Z
=
206
82
Pb
82
4
2
4
2
He
Beta Emission
Occurs when there’s too many neutrons in nucleus. A
neutron is converted into a proton & an electron.
Only the electron is then emitted.
131
53
I
131
54
Xe  e
0
-1
electron
Beta Emission
Ex. Polonium-210 undergoes beta decay to produce
this daughter nuclide. What is the daughter nuclide?
210
84
Atomic Mass:
Po
210
-
210
Atomic #:
A
Z
0
=
=
1
=
=
84
84
A
Z
+
X
=
X
+
A
A
0
+
-1
=
210
Z
+
Z
=
210
85
At
85
0
-1
e
Gamma Emission
Occurs when a high energy wave is emitted from the
nucleus of an unstable atom.
Emission of high energy changed the nucleus
from an unstable state to a stable state.
Gamma Emission
Ex. Polonium-210 undergoes gamma decay to produce
this daughter nuclide
210
84
Atomic Mass:
Atomic #:
A
Z
Po
A
=
=
Z
=
=
210
84
A
Z
X
=
X
+
0
0
A
+
0
Z
+
0
210
84
210
84
Po

Types of Radiation
• Alpha particle ()
– helium nucleus
• Beta particle (-)
– electron
• Gamma ()
– high-energy photon
4
2
Charge Shielding
He
2+
paper
0
-1
1-
Al
e
concrete
0
0

0
lead
Is ALL radiation bad?
Using a Geiger Counter to measure
background radiation
Alpha particles are used in smoke alarms
Smoke free
In the smoke-free chamber,
positive and negative ions
create a small current as they
migrate to charged plates
Smoke present
When smoke is present, fewer
ions are available to migrate to
the plates, the disrupted
current triggers the alarm
Beta radiation is used in industry to
detect thicknesses of materials
Radiation is used in industry in detectors that monitor and control the
thickness of materials such as paper, plastic and aluminium. The thicker
the material, the more radiation is absorbed and the less radiation reaches
the detector. It then sends signals to the equipment that adjusts the
thickness of the material.
Gamma rays can also be used to
sterilise medical equipment
Radiation can also be harmful
Beta particles and gamma rays are the most dangerous outside the
human body.
Radiation from alpha particle sources is the most dangerous inside
the human body.
Cut and paste activity – How much do
you remember?
Type of
Radiation
Symbol
Mass (amu)
Charge
Speed
Ionising
ability
Penetrating
power
Stopped by:
Alpha
particle
Beta particle Gamma ray
Memorise the information on this table
Type of
Radiation
Symbol
Alpha particle
or
or
Beta particle
Gamma ray
or
or
Mass (amu)
4
1/2000
0
Charge
+2
-1
0
Speed
slow
fast
very fast (speed
of light)
Ionising ability
high
medium
0
Penetrating
power
low
medium
high
Stopped by:
paper
aluminium
lead
Radioactivity
Radioactive elements decay at a constant
rate, because radioactive decay is not
affected by changes in temperature,
pressure, pH, etc.
Therefore, we can use radioactive elements
to determine the age of fossils and rock
strata.