RADIOACTIVE ELEMENTS

Nuclear reactions – reactions that involve the particles in the nucleus of an atom.

Isotopes – an atom with the same number of protons and different numbers of neutrons.

Isotopes are designated by using the name of the element and its mass number.

Mass number – the sum of the protons and neutrons in the nucleus of

an atom.(examples: carbon-12, carbon-

14, uranium-238)

mass number 14C

atomic number 6

Radioactive decay – a process by which the atomic nuclei of unstable isotopes release fast-moving particles and energy.

Radioactive decay can produce 3 forms of nuclear radiation:

(1) alpha particles(2) beta particles(3) gamma rays

Alpha Decay

Alpha particle – consists of two protons and two neutrons (same as a helium nucleus).

*Release of an alpha particle decreases the atomic number by 2 and the mass number by 4.

Alpha particles are the least penetrating of the forms of nuclear radiation.

Alpha Decay

Beta DecayBeta decay occurs when a neutron breaks apart, forming a beta particle and a proton.

Beta particle – a high energy electron given off during beta decay.

Beta decay results in the mass number remaining the same and the atomic number increasing by one.

Beta particles may travel into the human body and damage cells.

Beta Decay

Gamma Decay

Gamma radiation is high energy waves, similar to X-rays. Alpha and beta decay are almost always accompanied by gamma radiation.

Gamma rays do not cause a change in either the atomic mass or the atomic number.

Gamma rays are the most penetrating type of radiation. They can pass right through the human body causing severe damage to cells.

Penetrating Power of Radiation

Half Life

Half-life – the length of time needed for half the atoms of a radioactive isotope to decay.

The half-life of each radioactive isotope differs [Figure 21 – page 92].

The half-life of certain radioactive isotopes can be used by scientists to determine the ages of rocks and fossils found in them = radioactive dating.

Carbon-14 can be used to determine the age of objects up to 60,000 years. Older objects require the use of potassium-40 and uranium-238.

Using Radioactive Isotopes

Tracers- radioactive isotopes that can be followed through the steps of a chemical reaction or industrial process.

Medical uses include the identification and treatment of diseases.

Radiation therapy involves the use of radioactive elements to destroy unhealthy cells (cancer treatment).

Nuclear Power

Some power plants use radioactive isotopes as fuel to produce electricity (uranium-235).

Dangers of Radioactive Materials

Exposure to radiation can cause illness, disease, and possibly death.

People working with radioactive materials must wear protective clothing and shields.

Radioactive wastes must be buried in specially-constructed underground waste isolation tunnels.