CHAPTER 10 Nuclear Chemistry General, Organic, & Biological Chemistry Janice Gorzynski Smith

1. CHAPTER 10 Nuclear Chemistry General, Organic, & Biological Chemistry Janice GorzynskiSmith

2. CHAPTER 10: Nuclear Chemistry Learning Objectives: • Interpret Atomic number and mass number • Know radioactive particles: alpha, beta, positron, gamma • Write & solve radioactive decay equations • Determine the number of half lives that pass in a given amount of time. • Familiar with measurements of the amount of radioactivity • Familiar with measurements of radiation absorbed • Understand how radioisotopes are used in medicine Smith. General Organic & BiologicialChemistry 2nd Ed.

3. Nuclear Chemistry Isotope Review atomic number (Z) = the number of protons the number of protons mass number (A) = + the number of neutrons mass number (A) 12 C 6 atomic number (Z) number of protons 6 12 – 6 = 6 number of neutrons Smith. General Organic & Biological Chemistry 2nd Ed.

4. Nuclear Chemistry Radioactive Isotopes • A radioactive isotope, called a radioisotope, is • unstable and spontaneously emits energy to form • a more stable nucleus. • Radioactivity is the nuclear radiation emitted by a • radioactive isotope. • Of the known isotopes of all elements, 264 are stable and 300 are naturally occurring but unstable. • An even larger number of radioactive isotopes, called artificial isotopes, have been produced in the laboratory. Smith. General Organic & Biological Chemistry 2nd Ed.

5. 4 He 2 1 1 1 1 0 0 0 0 n n p p e e e e 1 0 1 0 −1 −1 +1 +1 Nuclear Chemistry Radiation alpha particle: a or  Alpha particles are helium isotopes with 2 extra neutrons  Beta particles are formed from neutrons beta particle: βor + proton  particle neutron  Positrons are formed from protons positron: β+ or + positron neutron proton gamma ray: g  A form of energy with no mass or charge Smith. General Organic & Biological Chemistry 2nd Ed.

6. Nuclear Chemistry Nuclear Reactions Radioactive decayis the process by which an unstable radioactive nucleus emits radiation. A nuclear equation can be written as: original nucleus new nucleus radiation emitted + The following must be equal on both sides of a nuclear equation: • The sum of the mass numbers (A) • The sum of the atomic numbers (Z) Smith. General Organic & Biological Chemistry 2nd Ed.

7. Nuclear Chemistry Nuclear Reactions Alpha emission is the decay of a nucleus by emitting an a particle. Smith. General Organic & Biological Chemistry 2nd Ed.

8. Nuclear Chemistry Nuclear Reactions Beta emission is the decay of a nucleus by emitting a βparticle; 1 neutron is lost and 1 proton is gained. Smith. General Organic & Biological Chemistry 2nd Ed.

9. Nuclear Chemistry Nuclear Reactions Positron emission is the decay of a nucleus by emitting a positron, β+; 1 proton is lost and 1 neutron is gained. Smith. General Organic & Biological Chemistry 2nd Ed.

10. Nuclear Chemistry Nuclear Reactions Gamma emission is the decay of a nucleus by emittingg radiation. • The g rays are a form of energy only. • Their emission causes no change in the atomic • number or the mass number. 99m 99 g + Tc Tc 43 43 Commonly, g emission accompanies a or β emission. Smith. General Organic & Biological Chemistry 2nd Ed.

11. Nuclear Chemistry Half-Life The half-life (t1/2) of a radioactive isotope is the time it takes for one-half of the sample to decay. The half-life of a radioactive isotope is a property of a given isotope and is independent of the amount of sample, temperature, and pressure. Smith. General Organic & Biological Chemistry 2nd Ed.

12. Nuclear Chemistry Half-Life Smith. General Organic & Biological Chemistry 2nd Ed.

13. Nuclear Chemistry Detecting & Measuring Radioactivity The amount of radioactivity in a sample is measured by the number of nuclei that decay per unit time: disintegrations per sec. • Common units include: 1 Curie (Ci) = 3.7 x 1010 disintegrations/second 1 becquerel (Bq) = 1 disintegration/second 1 Ci = 3.7 x 1010Bq. Several units are used to measure the amount of radiation absorbed by an organism. • The rad—radiation absorbed dose—is the amount of radiation absorbed by one gram of a substance. • The rem—radiation equivalent for man—is the amount of radiation that also factors in its energy and potential to damage tissue. Smith. General Organic & Biological Chemistry 2nd Ed.

14. Nuclear Chemistry Detecting & Measuring Radioactivity • The average radiation dose per year for a person • is about 0.27 rem. • Generally, no detectable biological effects are • noticed for a radiation dose less than 25 rem. • A single dose of 25–100 rem causes a temporary • decrease in white blood cell count. • A dose of more than 100 rem causes radiation • sickness—nausea, vomiting, fatigue, etc. • The LD50—the lethal dose that kills 50% of a • population—is 500 rem in humans, while 600 rem is fatal for an entire population. Smith. General Organic & Biological Chemistry 2nd Ed.

15. Nuclear Chemistry Radioisotopes Used in Medicine • Radioisotopes can be injected or ingested to • determine if an organ is functioning properly or • to detect the presence of a tumor. • Technetium-99m is used to evaluate the gall • bladder and bile ducts and to detect internal • bleeding. • Thallium-201 is used in stress tests to diagnose • coronary artery disease. • Using a scan, normal organs are clearly visible, • while malfunctioning or obstructed organs are not. Smith. General Organic & Biological Chemistry 2nd Ed.

16. Nuclear Chemistry Radioisotopes Used in Medicine Smith. General Organic & Biological Chemistry 2nd Ed.

17. Nuclear Chemistry Radioisotopes Used in Medicine Smith. General Organic & Biological Chemistry 2nd Ed.

18. Nuclear Chemistry Radioisotopes Used in Medicine • Positron emission tomography (PET) scans use radioisotopes which emit positrons which enable scanning of an organ. • PET scans can detect tumors, coronary artery disease, Alzheimer’s disease, and track the progress of cancer. • A PET scan is a noninvasive method of monitoring cancer treatment. Smith. General Organic & Biological Chemistry 2nd Ed.