Review Atomic Number (Z) – number of protons Mass Number (A) – sum of protons and neutrons Copyright © Cengage Learning. All rights reserved

Radioactive Decay Nucleus undergoes decomposition to form a different nucleus. Nuclides with 84 or more protons are unstable. Copyright © Cengage Learning. All rights reserved

The Zone of Stability Copyright © Cengage Learning. All rights reserved

Types of Radioactive Decay Alpha production (α): Beta production (β): Copyright © Cengage Learning. All rights reserved

Types of Radioactive Decay Gamma ray production (γ): Positron production: Copyright © Cengage Learning. All rights reserved

Types of Radioactive Decay Electron capture: Inner-orbital electron Copyright © Cengage Learning. All rights reserved

Decay Series (Series of Alpha and Beta Decays) Copyright © Cengage Learning. All rights reserved

Balancing Nuclear Equations Conserve mass number (A). The sum of protons plus neutrons in the products must equal the sum of protons plus neutrons in the reactants. 1n U 235 92 + Cs 138 55 Rb 96 37 + 2 235 + 1 = 138 + 96 + 2x1 Conserve atomic number (Z) or nuclear charge. The sum of nuclear charges in the products must equal the sum of nuclear charges in the reactants. 1n U 235 92 + Cs 138 55 Rb 96 37 + 2 92 + 0 = 55 + 37 + 2x0

Which of the following produces a particle? electron capture positron CONCEPT CHECK! Which of the following produces a particle? electron capture positron alpha particle beta particle The correct answer is d. Go through the rest of the equations to identify these types of equations as well. Copyright © Cengage Learning. All rights reserved

19.1 Balance the following nuclear equations (that is, identify the product X): (a) (b)

19.1 Strategy In balancing nuclear equations, note that the sum of atomic numbers and that of mass numbers must match on both sides of the equation. Solution (a) The mass number and atomic number are 212 and 84, respectively, on the left-hand side and 208 and 82, respectively, on the right-hand side. Thus, X must have a mass number of 4 and an atomic number of 2, which means that it is an α particle. The balanced equation is

19.1 (b) In this case, the mass number is the same on both sides of the equation, but the atomic number of the product is 1 more than that of the reactant. Thus, X must have a mass number of 0 and an atomic number of -1, which means that it is a β particle. The only way this change can come about is to have a neutron in the Cs nucleus transformed into a proton and an electron; that is, (note that this process does not alter the mass number). Thus, the balanced equation is

Rate of Decay Rate = kN The rate of decay is proportional to the number of nuclides. This represents a first-order process. Copyright © Cengage Learning. All rights reserved

Half-Life Time required for the number of nuclides to reach half the original value. Copyright © Cengage Learning. All rights reserved

Nuclear Particles To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE Copyright © Cengage Learning. All rights reserved

Half-Life of Nuclear Decay To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE Copyright © Cengage Learning. All rights reserved

EXERCISE! A first order reaction is 35% complete at the end of 55 minutes. What is the value of k? ln[A] = –kt + ln[A]o ln(0.65) = –k(55) + ln(1) k = 7.8 × 10-3 min-1 k = 7.8 x 10-3 min-1. If students use [A] = 35 in the integrated rate law (instead of 65), they will get k = 1.9 x 10-2 min-1. Note: Use the red box animation to assist in explaining how to solve the problem.

Nuclear Transformation The change of one element into another. (Happens by bombarding the nucleus, here with alpha particle or another element) Copyright © Cengage Learning. All rights reserved

Accelerators like cyclotron and linear accelerators is used to bombard a nucleus with high velocity positive ion to produce other element Neutrons are also used for this purpose

Measuring Radioactivity Levels Geiger counter Scintillation counter Copyright © Cengage Learning. All rights reserved

Geiger Counter To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE Copyright © Cengage Learning. All rights reserved

Carbon–14 Dating Used to date wood and cloth artifacts. Based on carbon–14 to carbon–12 ratio. Copyright © Cengage Learning. All rights reserved

Radiotracers Radioactive nuclides that are introduced into organisms in food or drugs and whose pathways can be traced by monitoring their radioactivity. Copyright © Cengage Learning. All rights reserved

Radiotracers Copyright © Cengage Learning. All rights reserved

Energy and Mass When a system gains or loses energy it also gains or loses a quantity of mass. E = mc2 Δm = mass defect ΔE = change in energy If ΔE is negative (exothermic), mass is lost from the system. Copyright © Cengage Learning. All rights reserved

Binding Energy The energy required to decompose the nucleus into its components. Iron-56 is the most stable nucleus and has a binding energy of 8.79 MeV. Copyright © Cengage Learning. All rights reserved

19.2 The atomic mass of is 126.9004 amu. Calculate the nuclear binding energy of this nucleus and the corresponding nuclear binding energy per nucleon.

19.2 Strategy To calculate the nuclear binding energy, we first determine the difference between the mass of the nucleus and the mass of all the protons and neutrons, which gives us the mass defect. Next, we apply Equation (19.2) [ΔE = (Δm)c2]. Solution There are 53 protons and 74 neutrons in the iodine nucleus. The mass of 53 atom is 53 x 1.007825 amu = 53.41473 amu and the mass of 74 neutrons is 74 x 1.008665 amu = 74.64121 amu

19.2 Therefore, the predicted mass for is 53.41473 + 74.64121 = 128.05594 amu, and the mass defect is Δm = 126.9004 amu - 128.05594 amu = -1.1555 amu The energy released is ΔE = (Δm)c2 = (-1.1555 amu) (3.00 x 108 m/s)2 = -1.04 x 1017 amu · m2/s2

19.2 Let’s convert to a more familiar energy unit of joules. Recall that 1 J = 1 kg · m2/s2. Therefore, we need to convert amu to kg: Thus, the nuclear binding energy is 1.73 x 10-10 J . The nuclear binding energy per nucleon is obtained as follows: (1.60 x 10-13 J = 1 MeV)

Binding Energy per Nucleon vs. Mass Number Copyright © Cengage Learning. All rights reserved

Nuclear Fission and Fusion Fusion – Combining two light nuclei to form a heavier, more stable nucleus. Fission – Splitting a heavy nucleus into two nuclei with smaller mass numbers. Copyright © Cengage Learning. All rights reserved

Nuclear Fission To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE Copyright © Cengage Learning. All rights reserved

Fission Processes A self-sustaining fission process is called a chain reaction. Copyright © Cengage Learning. All rights reserved

Schematic of a Nuclear Reactor

Schematic Diagram of a Reactor Core Copyright © Cengage Learning. All rights reserved

Nuclear Fusion To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE Copyright © Cengage Learning. All rights reserved

Biological Effects of Radiation Depend on: Energy of the radiation Penetrating ability of the radiation Ionizing ability of the radiation Chemical properties of the radiation source Copyright © Cengage Learning. All rights reserved

rem (roentgen equivalent for man) The energy dose of the radiation and its effectiveness in causing biologic damage must be taken into account. Number of rems = (number of rads) × RBE rads = radiation absorbed dose RBE = relative effectiveness of the radiation in causing biologic damage

Effects of Short-Term Exposures to Radiation Copyright © Cengage Learning. All rights reserved