THE NUCLEUS: A CHEMIST’S VIEW Chapter Eighteen: THE NUCLEUS: A CHEMIST’S VIEW

Review Atomic Number (Z) – number of protons Mass Number (A) – sum of protons and neutrons 18.1 Copyright © Houghton Mifflin Company. All rights reserved. 6

Radioactive Decay Nucleus undergoes decomposition to form a different nucleus. 18.1 Copyright © Houghton Mifflin Company. All rights reserved. 6

Radioactive Stability Nuclides with 84 or more protons are unstable. 18.1 Copyright © Houghton Mifflin Company. All rights reserved. 6

Radioactive Stability Light nuclides are stable when Z equals A – Z (neutron/proton ratio is 1). For heavier elements the neutron/proton ratio required for stability is greater than 1 and increases with Z. 18.1 Copyright © Houghton Mifflin Company. All rights reserved. 6

Radioactive Stability Certain combinations of protons and neutrons seem to confer special stability. Even numbers of protons and neutrons are more often stable than those with odd numbers. 18.1 Copyright © Houghton Mifflin Company. All rights reserved. 6

Radioactive Stability Certain specific numbers of protons or neutrons produce especially stable nuclides. 2, 8, 20, 28, 50, 82, and 126 18.1 Copyright © Houghton Mifflin Company. All rights reserved. 6

The Zone of Stability Copyright © Houghton Mifflin Company. All rights reserved.

Types of Radioactive Decay Alpha production (): Beta production (): 18.1 Copyright © Houghton Mifflin Company. All rights reserved. 1

Types of Radioactive Decay Gamma ray production (): Positron production: Electron capture: 18.1 Copyright © Houghton Mifflin Company. All rights reserved. 2

Decay Series (Series of Alpha and Beta Decays) Copyright © Houghton Mifflin Company. All rights reserved.

Nuclear Particles 18.2 Copyright © Houghton Mifflin Company. All rights reserved.

Nuclear Transformation The change of one element into another. 18.3 Copyright © Houghton Mifflin Company. All rights reserved. 6

A Schematic Diagram of a Cyclotron 18.3 Copyright © Houghton Mifflin Company. All rights reserved.

A Schematic Diagram of a Linear Accelerator Odd-numbered tubes are negatively charged, and the even-numbered tubes are positively charged. 18.3 Copyright © Houghton Mifflin Company. All rights reserved.

Measuring Radioactivity Levels Geiger counter Scintillation counter 18.4 Copyright © Houghton Mifflin Company. All rights reserved. 6

Geiger Counter 18.4 Copyright © Houghton Mifflin Company. All rights reserved.

Energy and Mass When a system gains or loses energy it also gains or loses a quantity of mass. E = mc2 m = mass defect E = change in energy If E is negative (exothermic), mass is lost from the system. 18.5 Copyright © Houghton Mifflin Company. All rights reserved. 7

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 8.97 MeV. 18.5 Copyright © Houghton Mifflin Company. All rights reserved. 8

Binding Energy per Nucleon vs. Mass Number 18.5 Copyright © Houghton Mifflin Company. 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. 18.6 Copyright © Houghton Mifflin Company. All rights reserved. 9

Nuclear Fission 18.6 Copyright © Houghton Mifflin Company. All rights reserved.

Fission Processes A self-sustaining fission process is called a chain reaction. 18.6 Copyright © Houghton Mifflin Company. All rights reserved. 10

Schematic Diagram of a Nuclear Power Plant 18.6 Copyright © Houghton Mifflin Company. All rights reserved.

Schematic Diagram of a Reactor Core Copyright © Houghton Mifflin Company. All rights reserved.

Nuclear Fusion 18.6 Copyright © Houghton Mifflin Company. 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 18.7 Copyright © Houghton Mifflin Company. All rights reserved. 13

Effects of Short-Term Exposures on Radiation 18.7 Copyright © Houghton Mifflin Company. All rights reserved.