General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 4.1 Natural Radioactivity Chapter 4 Nuclear Chemistry © 2013 Pearson Education, Inc. Lectures

© 2013 Pearson Education, Inc. Chapter 4, Section 1 2 Radioactive Isotopes A radioactive isotope  has an unstable nucleus and usually has an atomic number above 20.  emits radiation to become more stable.  can be one or more of the isotopes of an element.  is identified by writing the mass number after the element symbol, such as iodine-131 or I-131.  has the following symbol:

© 2013 Pearson Education, Inc. Chapter 4, Section 1 3 Some Stable and Radioactive Isotopes

© 2013 Pearson Education, Inc. Chapter 4, Section 1 4 Types of Radiation Radiation is the energy emitted by an unstable atom in the process of becoming more stable. It takes the form of  alpha particles, which are identical to a helium nucleus,  beta particles, which are high-energy electrons with a charge of 1− and a mass number of 0,

© 2013 Pearson Education, Inc. Chapter 4, Section 1 5 Types of Radiation (continued)  positron, similar to a beta particle with a charge of 1+ and mass number of 0, and  gamma rays, which are high-energy radiation often emitted with other types of radiation. They are written with a mass and atomic number of 0.

© 2013 Pearson Education, Inc. Chapter 4, Section 1 6 Summary, Types of Radiation

© 2013 Pearson Education, Inc. Chapter 4, Section 1 7 Biological Effects of Radiation  When radiation strikes molecules, electrons may be knocked away, forming unstable ions.  If this ionizing radiation passes through the human body, it may interact with water molecules, removing an electron, producing H 2 O +.  H 2 O + can cause undesirable chemical reactions damaging cells.

© 2013 Pearson Education, Inc. Chapter 4, Section 1 8 Radiation Protection Radiation protection requires  paper and clothing for alpha particles,  a lab coat or gloves for beta particles,  a lead shield or a thick concrete wall for gamma rays,  limiting the amount of time spent near a radioactive source, or  increasing the distance from the source.

© 2013 Pearson Education, Inc. Chapter 4, Section 1 9 Shielding for Radiation Protection

© 2013 Pearson Education, Inc. Chapter 4, Section 1 10 Learning Check What shielding is required to protect from the following forms of radiation? 1. Alpha radiation 2. Gamma radiation

© 2013 Pearson Education, Inc. Chapter 4, Section 1 11 Solution What shielding is required to protect from the following forms of radiation? 1. Alpha radiation requires paper or clothing for. protection. 2. Gamma radiation requires a lead shield for. protection.

© 2013 Pearson Education, Inc. Chapter 4, Section 1 12 Learning Check Which form of radiation emitted has a mass number of 0 and a positive charge? Give its name and symbol.

© 2013 Pearson Education, Inc. Chapter 4, Section 1 13 Solution Which form of radiation emitted has a mass number of 0 and a positive charge? Give its name and symbol. Solution: Positron