NUCLEAR VS. CHEMICAL
• CHEMICAL reactions involve
rearranging of atoms: e.g., H2 +O2  H2O
• No new atoms are created.
• Chemistry involves electrons only.
CHEMICAL VS. NUCLEAR
• NUCLEAR reactions involve taking atoms
apart and making new atoms.
• Nuclear reactions involve protons and
neutrons (the stuff in the nucleus!)
NUCLEAR DECAY
• NOTE: decay doesn’t mean the mass is
“gone,” just that the atoms have become
different atoms.
• What law discusses this???
UNSTABLE atoms DECAY--they emit
energy (radiation) to become more stable.
RF mwave infrared visible uv x-ray g-ray cosmic
LOW ENERGY
Non-ionizing
HIGH ENERGY
Ionizing radiation
MOST isotopes are RADIOACTIVE (unstable)-nearly 85% of all
known isotopes decay…only about 15% are
STABLE.
Ionizing Radiation
Can deposit energy in neighboring atoms
resulting in the removal of electrons
IONIZING RADIATION
• Since your cells and tissues are
NEUTRAL, ionizing radiation is NOT
GOOD.
Type of Radiation
Alpha
Beta
Gamma
Neutron
Greek
Symbol
Chemical
Symbol
Charge
Shielding/
Protection
Additional Information
Alpha Particle
Consists of two protons and two neutrons.
Just like a He nucleus (no electrons)
It has a charge of +2: it is IONIZING.
They have a low penetrating power - can be stopped
by your skin.
4
2
4
2
He
α
Chemical Symbol
Greek Symbol
He
Alpha Particle
 Alpha particles are relatively slow and heavy.
 Rapidly lose energy when passing through matter.
 Does not penetrate very far, but can cause damage over
its short path through tissue.
 Can be very harmful if ingested or inhaled.
Alpha radiation is only a hazard when
inside your body (internal hazard)
Can’t penetrate skin
Internal hazard
Stopped by paper
Found in soil, radon and
other radioactive materials
Beta Particle
 Fast moving electrons emitted from the nucleus
during radioactive decay.
?? IONIZING or NOT ??
More penetrating than an Alpha Particle
Can penetrate skin, but more hazardous when inhaled.
ELECTRON
Can be slowed or stopped by a layer of clothing
or a few
mm of aluminum.
0
-1 e
Chemical Symbol

Greek Symbol
Beta radiation is a skin,
eye and internal hazard
Skin, eye and internal hazard
Stopped by clothing/aluminum
Found in natural
food, air and water
Gamma Radiation
g
• Gamma rays are waves of energy, not particles. They
have no mass and no charge, but are ionizing.
• Often produced with alpha or beta particles.
• Gamma rays can easily pass through the body or be
absorbed by tissue, thus a hazard for the entire body.
• Gamma rays have a high penetrating power - it takes
a thick sheet of lead or concrete to slow them down.
• Gamma rays are like X-rays, only more energetic.
Gamma radiation is penetrating radiation
and an EXTERNAL HAZARD
Stopped by several inches of lead or
several feet of concrete.
Naturally present in soil
and cosmic radiation
Many medical uses
Neutron
Neutrons are the most penetrating.
Have mass, but no charge (IONIZING??)
On Earth they mostly come from the splitting,
or fissioning, of atoms inside a nuclear reactor.
Water and concrete are the most commonly used
shields against neutron radiation from the core of
the nuclear reactor.
1
n
0
What are health risks
from ionizing radiation?
• The degree of damage caused by radiation depends
– dose
– dose rate
– type of radiation
– the part of the body exposed
– age and health
• Large doses of ionizing radiation can cause various
forms of cancers. At very high levels, radiation can
cause sickness and death.
• The body has defense mechanisms against low levels of
radiation.
• Radiation therapy is used to kill cancerous cells.
• Much larger doses are used to kill harmful bacteria in
food (without leaving radioactive “residue,”) and to
sterilize bandages and other medical equipment.
Radiation Dose
• Naturally occurring background radiation is
the main source of exposure for most
people.
• Background radiation comes from three
sources:
– cosmic rays
– naturally occurring radioactive elements
such as radon-222
– solar radiation.
– The amount of background radiation
depends on factors like location, house
construction materials, medical treatments,
and occupation.
– The average exposure for a U.S. resident is
0.36 rem per year.
Radioactive Decay
Not all isotopes are
“finished” after they decay.
Some products are also
radioactive, and the
matter will not
be stable until many
decay steps
have occurred.
Type of Radiation
Alpha
Greek
Symbol
a

Shielding/
Protection
Additional Information
He
+2
1 sheet
of paper
Low penetrating power; is a
helium nucleus; slow and
heavy
e
-1
Layer of
clothing,
alum.,
plastic
Fast moving electron; result
is to change a neutron into a
proton; penetrates skin,
eyes; is an internal hazard
none
none
Lead,
concrete
High penetrating power;
hazard for entire body; often
accompanies a,or 
1
none
Water,
concrete
Nuclear power comes from
Uranium neutron decay.
4
0
-1
1 electron
Gamma
Charge
2
2 protons
2 neutrons
Beta
Chemical
Symbol
g
Not a particle;
a wave
Neutron
none
0
n