UNSTABLE NUCLEI & RADIOACTIVE DECAY

Bell Work  Read Section 4.4 page

Objectives:  Examine the relationship between unstable nuclei & radioactive decay.  Characterize Alpha, Beta, and Gamma Radiation.

SPI’s/CLE’s:  CLE Describe an atom in terms of its composition and electron characteristics.  CLE Analyze chemical and nuclear reactions.  SPI Describe radioactive decay through a balanced nuclear equation and through an analysis of the half-life concept.  SPI Compare and contrast nuclear fission and fusion.

Back Ground Information:  3 major kinds of changes: 1. Physical 2. Chemical 3. Nuclear

What is Radioactivity?  The process in which substances spontaneously emit radiation.  Radiation – the rays & particles emitted by radioactive material.

What is Radioactive Decay?  Process in which unstable nuclei lose energy by emitting radiation.

Types of Radiation:  Alpha - contains two protons and two neutrons; + 2 charge.  Beta – an electron; - 1 charge  Gamma – high energy; has no mass & no charge.

What determines Nuclear Stability?  Atoms that contain too few or too many neutrons are unstable and undergo radioactive decay to create a stable nucleus.  Atoms with an atomic number higher than 82 are considered unstable and will undergo radioactive decay.

Classify the following as a chemical reaction, nuclear reaction or neither:  Thorium emits a beta particle.  Two atoms share electrons to form a bond.  A sample of pure sulfur emits heat energy as it slowly cools down.  A piece of iron rusts.

Enrichment: Did you Know?  Naturally occurring radioactive material, is found almost everywhere. It is found in the air and in soil, and even in radioactive potassium in our own bodies. It is found in public water supplies and foods such as brazil nuts, cereal, and peanut butter.  The average person in the United States is exposed to about 360 millirems of radiation from natural sources each year. A millirem, or one one-thousandth of a rem, is a measure of radiation exposure.  Consumer products contribute 10 millirem/year, while living or working in a brick building can add another 70 millirem/year. A person who smokes one and a half packs of cigarettes per day increases his or her exposure by 8000 millirem/year.

Homework:  Find at least one everyday application of radiation.  Find how much radiation a human body can undergo before the cells begin to deteriorate.  Find a naturally occurring radioactive element.