Chapter 19 Radioactivity

Chapter 19:1 Fun Fact: If the nucleus of the hydrogen atom was a ping pong ball, the electron in the 1s orbital would be 0.3 mile away and have a mass of 2.5 billion tons. The energies involved in nuclear processes are typically millions of times larger than those associated with normal chemical reactions.

Chapter 19:1 Nucleons: particles of neutrons and protons. Atomic #: # of protons. Mass #: # of protons + neutrons. Atoms that have identical atomic # but different mass numbers are called isotopes. Nuclide: applied to each unique atom

Chapter 19:1 Carbon 12 C 13 C 14 C Many nuclei are radioactive: they spontaneously decompose. 14 C 14 N + 0 e where e, represents an electron, which is called a beta  particle Both the atomic number and the mass number must be equal.

19.1: Types of Radioactive Decay Alpha (  ) particle: a helium nucleus 4 He A very common mode of decay for heavy radioactive nuclides. Radium-222 to give Radon Ra 4 He Rn 230 Th 4 He+ 226 Ra

19.1: Types of Radioactive Decay Beta (  ) particle: 0 e The net effect of  -particle production is to change a neutron to a proton. Results in no change in mass number and an increase in 1 in atomic number 234 Th 234 Pa + 0 e 131 I 131 Xe + 0 e

19.1: Types of Radioactive Decay Gamma ray(  ): high-energy photon of light. Zero charge and zero mass number. 238 U 234 Th + 4 He+ 2 0  `

19.1: Types of Radioactive Decay Positron: particle w/ same mass as the electron but the opposite charge. 0 e +1

19.1: Types of Radioactive Decay Electron capture: a process by which one of the inner-orbital electrons is captured by the nucleus. 201 Hg + 0 e 201 Au + 0  `

19.3: Detection of Radioactivity and Concept of Half-life. Objectives: To learn about radiation detection instruments. To understand half-life.

Figure 19.2: A representation of a Geiger-Müller counter (Geiger). Ar(g) Ar + (g) + e - Argon doesn’t conduct a current, “pulse”

19.3: Detection of Radioactivity and Concept of Half-life. Scintillation counter: uses sodium iodide (gives off light) when struck by a high-energy particle. Detector senses the flashes of light and counts the decay events. Half-life: time required for half of the original sample of nuclei to decay.

Uses of Radioactivity 19.4: Dating by Radioactivity. Objectives: To learn how objects can be dated by radioactivity Carbon-14 dating: can be used to date wood and cloth artifacts. Reacts with oxygen to form carbon dioxide. Half-life of 5730 years.

Uses of Radioactivity 19.5: Medical Applications of Radioactivity. Objectives: To discuss the use of radiotracers in medicine. Radiotracers-radioactive nuclides that can be introduced into organisms in food or drugs. Examples: Iodine-131: illnesses of the thyroid. Thallium-201 damage to the heart muscle after a heart attack. Technetium-99 similar. Table 19-4 p. 619

Uses of Radioactivity 19-6: Nuclear Energy Fusion: combining 2 light nuclei to form a heavier nucleus. Fission: splitting a heavy nucleus into 2 nuclei

Figure 19.4: Unstable nucleus.

Figure 19.5: Representation of a fission process.

Figure 19.6: Diagram of a nuclear power plant.

Figure 19.7: Schematic of the reactor core.

Figure 19.8: Radioactive particles and rays vary greatly in penetrating power. 1.The Energy of the radiation 2.The penetrating ability of the radiation 3.Ionizing ability of the radiation 4.Chemical properties of the radiation. Total amount of mRem 125/year Human activities: 67 mrem