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 wave infrared visible uv x-ray -ray cosmic

LOW ENERGY HIGH ENERGY

Non-ionizing Ionizing radiation

MOST isotopes are RADIOACTIVE (unstable)--nearly 85% of allknown isotopes decay…only about 15% are STABLE.

Ionizing RadiationCan 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 Greek Symbol

Chemical Symbol

Charge Shielding/ Protection

Additional Information

Alpha

Beta

Gamma

Neutron

Alpha ParticleConsists 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.

He4

2

He4

2

Greek SymbolChemical Symbol

α

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.

Can be slowed or stopped by a layer of clothing or a few mm of aluminum.

ELECTRON

-0-1

eChemical 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• 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.

Stopped by several inches of lead or several feet of concrete.

Naturally present in soil and cosmic radiation

Many medical uses

Gamma radiation is penetrating radiation and an EXTERNAL HAZARD

NeutronNeutrons 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.

10n

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 alsoradioactive, and the matter will not be stable until many decay stepshave occurred.

Type of Radiation Greek Symbol

Chemical Symbol

Charge Shielding/ Protection

Additional Information

Alpha2 protons

2 neutrons

4 He2

+2 1 sheet of paper

Low penetrating power; is a helium nucleus; slow and

heavy

Beta1 electron

0 e -1

-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

GammaNot a particle; a wave

none none Lead, concrete

High penetrating power; hazard for entire body; often

accompanies or

Neutron none 1 n 0

none Water, concrete

Nuclear power comes from Uranium neutron decay.