A short introduction to the discovery, identity and health effects of the three typical radiations found in nature. Suitable for general or pre-AP chemistry.

1. The Alpha-Beta Mystery
TEKS Par 112.35 #12a

2. Becquerel's Mysterious Rock
 Henri Becquerel (Beck-uh-REL)
owned a rock of Uranium ore. It
appeared to give off a small amount
of heat.
 He took an unexposed photographic
plate and wrapped it so no visible
light could get to it.
 He put the rock on top of it and left it
in a desk drawer overnight.
Wikipedia

3. When he developed the plate, this is
what he saw:
Discussion: what do you think
had happened?

4. We Infer What Must Have Happened
 Visible light could not get through
 But some kind of light rays did get through
to cause the chemical reaction to occur and
the image to develop
 Later experiments showed that the
radiation was high energy, high frequency,
and short wavelength.
 The Uranium ore was RADIOACTIVE.

5. Marie & Pierre Curie. . .meanwhile
 Polish scientist Marie Curie and French
scientist Pierre Curie also worked with
uranium, radium, and thorium.
 They discovered a lower-energy ray
they called “alpha” rays, that could not
penetrate a sheet of paper.
 Later work showed the alpha rays
actually were helium ions.

6. Becquerel's Radiation
 Becquerel's rays DID penetrate paper.
 Could they be alpha rays/helium?
 Alpha rays do not penetrate paper
 Becquerel's rays can be bent by a
magnetic field, or electric field.
 So they must be charged particles
 Becquerel's rays are negatively charged
and very small, very fast.
 What particle of the atom could they be?

7. What Are They?
 Beta rays are fast-moving electrons
 Alpha rays are slow-moving helium ions
 Both types of radiation are charged
 Both types can be harmful

8. “Radium Girls”
The Radium Girls were female factory
workers who contracted radiation
poisoning from painting watch dials with
glow-in-the-dark paint at the United
States Radium factory in Orange, New
Jersey, around 1917.
The women, who had been told the
paint was harmless, ingested deadly
amounts of radium by licking their
paintbrushes to give them a fine point.
Many became sick; we don't know how
many died.
Story in NY Times, Oct 6, 1998
Wikipedia photo
Extension:
what kind of
radiation made
the young
women sick?

9. Another Radium Ray
 About 1898, French scientist Paul
Villard (Vil-AHRD) found that even
after all the alpha and beta radiation
was blocked, radium still exposed X-ray
film.
 He had discovered a third kind of
radiation from the atom.
 It was called gamma radiation, and
can only be shielded by several cm of
lead, or thick concrete.

10. Radiation Summary
Type of
Radiation
What
Is
It?
Mass
amu
Charge Protection
From
Effects
Alpha
α
Helium
Ion
(nucleus)
4 +2 Sheet of
paper
(don't
ingest!)
Beta
β
Electron
(e-)
1
1800
-1 Sheet of
metal (don't
ingest!)
Gamma
γ
High
energy,
Short
wavelength
Light
0 0 Thick lead
or
concrete