7-8 Nuclear Landscape

7-8 Nuclear Landscape - 1 CHEM 112 LRSVDS Nuclear part 2...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 CHEM 112 LRSVDS Nuclear part 2 Rules: 1) Up to atomic number 20 , n=p is stable. 2) Above atomic number 20 , n>p is stable. 3) Above atomic number 83 (Bi), all nuclei are unstable (radioactive). 4) Nuclei with 2, 8, 20, 28, 50, or 82 protons, or 2, 8, 20, 28, 50, 82, or 126 neutrons are particularly stable. These are the nuclear equivalent of closed shell configurations (and are called magic numbers ). 5) Even numbers of protons and neutrons are more stable. # of Stable Nuclei With This Configuration: # Protons # Neutrons 157 Even Even 52 Even Odd 50 Odd Even 5 Odd Odd NUCLEAR STABILITY 2 CHEM 112 LRSVDS Nuclear part 2 An isotope that is off the belt of stability can undergo one of four nuclear reactions to get to it: 1. ! decay 2. " decay 3. positron emission 4. electron capture The Belt of Stability 3 CHEM 112 LRSVDS Nuclear part 2 Getting Back to the Belt of Stability! 4 CHEM 112 LRSVDS Nuclear part 2 An isotope with a high n/p ratio is proton deficient . To convert neutrons to protons, it can undergo "-decay: 1 n # 97 40 Zr # NUCLEAR STABILITY: High neutron/proton ratio 5 CHEM 112 LRSVDS Nuclear part 2 i) Positron emission: 1 1 p # 1 n + 1 e ii) Electron capture: 1 1 p + 1 e # 1 n An isotope with a low n/p ratio is neutron deficient . To convert protons to neutrons, there are 2 possibilities: NUCLEAR STABILITY: Low neutron/proton ratio 11 20 Na " 60 141 Nd " 6 CHEM 112 LRSVDS Nuclear part 2 Nuclei with Atomic Numbers greater than or equal to 84 Undergo !- decay in order to reduce both the numbers of neutrons and protons: Example: 235 92 U # __________ + 4 2 5 CHEM 112 LRSVDS Nuclear part 2 i) Positron emission: 1 1 p # 1 n + 1 e ii) Electron capture: 1 1 p + 1 e # 1 n An isotope with a low n/p ratio is neutron deficient . To convert protons to neutrons, there are 2 possibilities: NUCLEAR STABILITY: Low neutron/proton ratio 11 20 Na " 60 141 Nd " 6 CHEM 112 LRSVDS Nuclear part 2 Nuclei with Atomic Numbers greater than or equal to 84 Undergo !- decay in order to reduce both the numbers of neutrons and protons: Example: 235 92 U # __________ + 4 2 He 7 CHEM 112 LRSVDS Nuclear part 2 ! Cascade of ! and " decay reactions ! Moves diagonally down belt of stability ! Eventually gets to a stable isotope (which one?) 238 U DECAY: Nuclear Disintegration Series 8 CHEM 112 LRSVDS Nuclear part 2 Nuclear Decay Summary !- decay element 1 # + element 2 AN >83 "-decay n/p high Positron n/p low light nuclei Electron n/p low Capture heavy nuclei 2 4 He 1 1 p " 1 n + + 1 e 1 n " 1 1 p + # 1 e 1 1 p + " 1 e # 1 n Reactants Products 9 CHEM 112 LRSVDS Nuclear part 2 Detection of Radioactivity Geiger Counter 10 CHEM 112 LRSVDS Nuclear part 2 Effects of Radiation 11 CHEM 112 LRSVDS Nuclear part 2 1987 Sources of Exposure to Radiation Average annual exposure (mrem) 50 100 Radon Source Natural Anthropogenic 200 mrem (55%) 39 mrem (11%) 27 mrem (8%) 28 mrem (8%) 40 mrem (11%) 14 mrem (4%) 11 mrem (3%) Rocks and Soil Cosmic Rays Radioisotopes in the body Medical X-rays...
View Full Document

Page1 / 20

7-8 Nuclear Landscape - 1 CHEM 112 LRSVDS Nuclear part 2...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online