Chemistry Notes

Nuclear Decay

Nuclear Radiation

Radioactivity: emission of rays or particles from the nucleus of an atom

Discovered by Henri Becquerel Saw uranium compounds caused white blurs

on photographic plates, even though they were wrapped in paper

Discovery Nuclear Radiation

Types of Radioactivity

Alpaha (α) Beta (β) Gamma (γ)

Types of Radioactivity

Alpha Radiation – emission of helium nuclei from the nucleus

Changes the mass of the atom Decreases by 4 amu

Result is the transformation of an atom into a lower element

Am-241 Np-237 + 42He

Alpha Radiation

Alpha radiation decrease the total mass by 4 and the number of protons by 2

Alpha Particles

The source of ionizing radiation is a minute quantity of americium-241 , which is a source of alpha particles (helium nuclei). The ionization chamber consists of two plates separated by about a centimeter. The battery applies a voltage to the plates, charging one plate positive and the other plate negative. Alpha particles constantly released by the americium knock electrons off of the atoms in the air, ionizing the oxygen and nitrogen atoms in the chamber. The positively-charged oxygen and nitrogen atoms are attracted to the negative plate and the electrons are attracted to the positive plate, generating a small, continuous electric current. When smoke enters the ionization chamber, the smoke particles attach to the ions and neutralize them, so they do not reach the plate. The drop in current between the plates triggers the alarm.

Types of Radioactivity

Beta Radiation – emission of electrons from the nucleus

Beta particles form when 1 neutron breaks down to form a proton and an electron No change in mass

Results is the transformation into a higher element Pa-91 0

-1e + U-92

Beta Radiation

Types of Radioactivity

Gamma Radiation – emission high energy electromagnetic waves from the nucleus

Gamma Radiation

Notice: There is no change in mass or the # of protons or neutrons

Determining Radiation

Types

Process of Radiation

Penetrability of Radiation Notice: different degrees of

penetrability between the radiation types Alpha (weakest) Gamma (strongest)

Practical Uses of Radioactive Elements Americium -241: Used in many smoke detectors for homes

and business...to measure levels of toxic lead in dried paint samples...to ensure uniform thickness in rolling processes like steel and paper production...and to help determine where oil wells should be drilled.

Californium - 252: Used to inspect airline luggage for hidden explosives...to gauge the moisture content of soil in the road construction and building industries...and to measure the moisture of materials stored in silos.

Copper - 67: When injected with monoclonal antibodies into a cancer patient, helps the antibodies bind to and destroy the tumor.

Krypton - 85: Used in indicator lights in appliances like clothes washer and dryers, stereos and coffee makers...to gauge the thickness of thin plastics and sheet metal, rubber, textiles and paper...and to measure dust and pollutant levels.

Thorium - 229: Helps fluorescent lights to last longer.

Medical Uses of Radioactive Elements Calcium - 47: Important aid to biomedical

researchers studying the cell function and bone formation of mammals.

Carbon - 14: Helps in research to ensure that potential new drugs are metabolized without forming harmful by-products.

Cesium - 137: Used to treat cancers...to measure correct patient dosages of radioactive pharmaceuticals...to measure and control the liquid flow in oil pipelines...to tell researchers whether oil wells are plugged by sand...and to ensure the right fill level for packages of food, drugs and other products.

Xenon - 133: Used in nuclear medicine for lung ventilation and blood flow studies.

Industrial Uses of Radioactive Elements

Curium - 244: Used in mining to analyze material excavated from pits slurries from drilling operations.

Iridium - 192: Used to test the integrity of pipeline welds, boilers and aircraft parts.

Nickel - 63: Used to detect explosives...and as voltage regulators and current surge protectors in electronic devices.

Sodium - 24: Used to locate leaks in industrial pipelines...and in oil well studies.

Radiation

Summary Definition and Discovery of Radiation Types of Radiation

Alpha / Beta /Gamma Identifying Radiation Types (diagram) Process of Radiation Uses of Radiation