1 Nuclear Radiation Natural Radioactivity A person working with radioisotopes wears protective clothing and gloves and stands behind a shield.

2 Radioactive Isotopes A radioactive isotope has an unstable nucleus emits radiation to become more stable can be one or more isotopes of an element is written with a mass number and an atomic number includes the mass number in its name Example: iodine-131

3 Examples of Radioactive Isotopes

4 Learning Check Thallium-201 is used for heart scans to determine cardiac function. A. How many protons are in thallium-201? B. How many neutrons are in thallium-201? C. What is the atomic symbol of thallium-201?

5 Nuclear Radiation Nuclear radiation is the radiation emitted by an unstable atom takes the form of alpha particles, neutrons, beta particles, positrons, or gamma rays

6 Alpha Particle An alpha (  ) particle has a helium nucleus 2 protons and 2 neutrons a mass number of 4 a charge of 2+ a low energy compared to other radiation particles

7 Beta Particle A beta (  ) particle is a high-energy electron has a mass number of 0 has a charge of 1- forms in an unstable nucleus when a neutron changes into a proton and an electron

8 Positron A positron (  + ) has a mass number of 0 has a charge of 1+ forms in an unstable nucleus when a proton changes into a neutron and a positron

9 Gamma (  ) Ray A gamma (  ) ray is high-energy radiation has a mass number of 0 has a charge of 0 is emitted from an unstable nucleus to give a more stable, lower energy nucleus

10 Summary of Common Forms of Nuclear Radiation

11 Learning Check Give the mass number and charge of each type of radiation. 1. alpha particle 2. positron 3. beta particle 4. neutron 5. gamma ray

12 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 increasing the distance from the source Radiation Protection

13 Radiation and Shielding Required

14 Radiation Protection Different types of shielding are needed for different radiation particles.

15 Learning Check Indicate the type of radiation (alpha, beta, and/or gamma) protection for each type of shielding. 1) heavy clothing 2) paper 3) lead 4) lab coat 5) thick concrete A person working with radioisotopes wears protective clothing and gloves and stands behind a shield.

16 Nuclear Radiation Nuclear Equations A radon gas detector is used to determine radon levels in buildings with inadequate ventilation.

Radioactive Decay In radioactive decay, a nucleus spontaneously emits radiation a nuclear equation is written for the radioactive nucleus, the new nucleus, and the radiation emitted Radioactive nucleus new nucleus + radiation ( , , ,  + ) 17

18 In a nuclear equation, the type of radiation emitted causes changes in the mass numbers changes in the atomic numbers for the nuclei of the unstable and stable nuclei Nuclear Equations

19 In a balanced nuclear equation, the sum of the atomic numbers for the nuclei of the reactant and the products must be equal Mass Numbers Total = 238 = 238 Total = 92 = 92 Atomic Numbers Balancing Nuclear Equations

20 Guide to Completing a Nuclear Equation

21 Alpha Decay In alpha decay, a radioactive nucleus emits an alpha particle to form a new nucleus that has a mass number 4 less than that of the initial nucleus an atomic number that has decreased by 2 from that of the initial nucleus

22 Example of Writing an Equation for Alpha Decay Write an equation for the alpha decay of STEP 1 Write the incomplete nuclear equation. STEP 2 Determine the missing mass number. 222 = ? – 4 = = ? (mass number of new nucleus)

23 Equation for Alpha Decay (continued) STEP 3 Determine the missing atomic number. 86 = ? – 2 = ? 84 = ? (atomic number of new nucleus STEP 4 Determine the symbol of the new nucleus. Symbol of element 84 = Po STEP 5 Complete the nuclear equation.

24 Beta Decay Beta decay occurs when an electron (beta particle) is emitted from the nucleus a neutron in the nucleus breaks down

25 Write an equation for the beta decay of potassium-42. STEP 1 Write the incomplete nuclear equation. STEP 2 Determine the missing mass number. 42 = ?  0 = 42 = ? (mass number of new nucleus) STEP 3 Determine the missing atomic number. 19 = ?  = ? 20 = ? (atomic number of new nucleus) Writing an Equation for a Beta Emitter

26 STEP 4 Determine the symbol of the new nucleus. Symbol of element 20 = Ca STEP 5 Complete the nuclear equation. Writing an Equation for a Beta Emitter (continued)

27 Write the nuclear equation for the beta decay of Xe-133. Learning Check

28 In positron emission, a proton is converted to a neutron and a positron the mass number of the new nucleus is the same, but the atomic number decreases by 1 Positron Emission

29 Write the nuclear equation for the positron emission by Rb-82. Learning Check

30 In gamma radiation, energy is emitted from an unstable nucleus, indicated by m following the mass number the mass number and the atomic number of the new nucleus are the same Gamma (  ) Radiation

31 Summary of Types of Radiation

32 Producing Radioactive Isotopes Radioactive isotopes are produced when a stable nucleus is converted to a radioactive nucleus by bombarding it with a small particle in a process called transmutation

33 What radioactive isotope is produced when a neutron bombards cobalt-59 and an alpha particle is emitted? Learning Check

34 Nuclear Radiation Radiation Measurement A radiation technician uses a Geiger Counter to check radiation levels.

35 Radiation Detection A Geiger counter detects beta and gamma radiation uses ions produced by radiation to create an electrical current

36 Radiation Measurement Radiation units of activity include curie (Ci) SI unit = becquerel (Bq) number of atoms that decay in one second 1 Ci = 3.7 x disintegrations/s 1 Ci = 3.7 x Bq rad (radiation absorbed dose) SI unit = gray(Gy) radiation absorbed by the tissues of the body 1 Gy = 100 rad rem (radiation equivalent) SI unit = sievert (Sv) biological damage caused by different types of radiation = absorbed dose (rad) x factor 1 Sv = 100 rem

37 Units of Radiation Measurement

38 Exposure to Radiation Exposure to radiation occurs from naturally occurring radioisotopes medical and dental procedures air travel, radon, and smoking cigarettes

Radiation Sickness 39 Radiation sickness depends on the dose of radiation received at one time is not detected under 25 rem involves a decrease in white blood cells at 100 rem includes nausea and fatigue over 100 rem reduces white-cell count to zero over 300 rem leads to death in 50% of people at 500 rem

40 Nuclear Radiation Half-Life of a Radioisotope The age of the Dead Sea scrolls was determined using carbon-14.

41 Half-Life The half-life of a radioisotope is the time for the radiation level (activity) to decrease (decay) to one-half of its original value.

42 Decay Curve A decay curve shows the decay of radioactive atoms the remaining radioactive sample

43 Half-lives of Some Radioisotopes Half-lives of radioisotopes that are naturally occurring tend to be long used in nuclear medicine tend to be short

44 In one half-life, 40 mg of a radioisotope decays to 20 mg. After two half-lives, 10 mg of radioisotope remain. 40 mg x 1 x 1 = 10 mg half-life 2 half-lives Initial 40 mg 20 mg 10 mg Half-Life Calculations

45 Examples of Half-Lives

46 Using Half-lives

47 The half-life of iodine-123 is 13 h. How much of a 64-mg sample of I-23 is left after 26 h? 1) 32 mg 2) 16 mg 3) 8 mg Learning Check

48 Nuclear Radiation Medical Applications Using Radioactivity

49 Medical Applications Radioisotopes with short half-lives are used in nuclear medicine because they have the same chemistry in the body as the nonradioactive atoms give off radiation that exposes a photographic plate (scan), giving an image of an organ

50 Using a Scanner to Detect Radiation (a) A scanner is used to detect radiation from a radioisotope that has accumulated in an organ. (b) A scan of the thyroid show the accumulation of radioactive iodine-131 in the thyroid.

Radioisotopes in Nuclear Medicine 51

52 Learning Check Which of the following radioisotopes are most likely to be used in nuclear medicine? 1) K-40 half-life 1.3 x 10 9 years 2) K-42 half-life 12 hours 3) I-131 half-life 8 days

53 Positron Emission Tomography (PET) In positron Emission Tomography (PET), positrons are emitted from positron emitters such as carbon -11, oxygen-15, and fluorine-18 positrons are used to study brain function and metabolism positrons combine with electrons to produce gamma ray that can be detected, giving a three- dimensional image

54 Positron Emission Tomography (PET) These PET scans of the brain show a normal brain on the left and a brain affected by Alzheimer’s disease on the right.

55 Computed Tomography (CT) In computed tomography (CT), X-rays are directed at the brain in layers are absorbed at different rates due to differences in densities of body tissues and fluids create three-dimensional images of the brain and any tumors or hemorrhages

56 Computed Tomography (CT) A CT scan shows a brain tumor (yellow) on the right side of the brain.

57 Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI) protons in the presence of a strong magnetic field align with the magnetic field protons release energy when magnetic field is removed protons in different environments emit energies of different frequencies to provide images of soft tissue

58 Magnetic Resonance Imaging (MRI) An MRI scan provides images of the heart and lungs.

59 Nuclear Radiation Nuclear Fission and Fusion

60 In nuclear fission, a large nucleus is bombarded with a small particle the nucleus splits into smaller nuclei and several neutrons large amounts of energy are released Nuclear Fission

61 Nuclear Fission When a neutron bombards U-235, an unstable nucleus of U-236 forms and undergoes fission (splits) smaller nuclei are produced such as Kr-91 and Ba-142 neutrons are released to bombard more U-235 nuclei

62 Nuclear Fission

63 Chain Reaction A chain reaction occurs when a critical mass of uranium undergoes fission releasing a large amount of heat and energy that produce an atomic explosion

64 Chain Reaction

65 Learning Check Supply the missing atomic symbol to complete the equation for the following nuclear fission reaction.

66 Nuclear Power Plants In nuclear power plants, fission is used to produce energy control rods in the reactor absorb neutrons to slow the fission process Nuclear power plants supply about 10% of the electricity in the United States.

67 Nuclear Power Plants

68 Nuclear Fusion Nuclear fusion occurs at extremely high temperatures ( °C) combines small nuclei into larger nuclei releases large amounts of energy occurs continuously in the sun and stars

69 Nuclear Fusion

70 Indicate if each of the following is 1) nuclear fissionor 2) nuclear fusion ___ A. a nucleus splits ___ B. large amounts of energy are released ___ C. small nuclei form larger nuclei ___ D. hydrogen nuclei react ___ E. several neutrons are released Learning Check

Concept Map 71