Nuclear chemistry

Subatomic Particles Protons- plus charge In the nucleus Neutrons- neutral Electrons - negative charge Outside the nucleus

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Stability of Nuclei http://www.eas.asu.edu/~holbert/eee460/decay.html Ratio of neutrons to protons determines stability = “belt of stability” Ratio of nuclei with atomic numbers greater than 83 makes those nuclei unstable (radioactive, radioisotope) Unstable nucleus decays forming products that are more stable; emits radiation

Radiation Radiation comes from the nucleus of an atom. Unstable nucleus emits a particle or energy  alpha  gamma  beta

Types of Radiation 2+ 1- 1+ Alpha particle () Beta particle (-) helium nucleus paper 2+ Beta particle (-) electron 1- lead Positron (+) positron 1+ concrete Gamma () high-energy photon

Alpha Emission Numbers must balance!! daughter nuclide parent nuclide particle Numbers must balance!!

Beta Emission Numbers must balance!! parent daughter electron nuclide

Positron Emission Numbers must balance!! parent daughter positron nuclide daughter nuclide positron Numbers must balance!!

Balancing Nuclear Equations 1) Use Table N to determine decay mode 2) In the reactants and products… Atomic and mass numbers must balance 3) A new element will be formed… according to the new atomic number

DECAY MODE

Learning Check 1 What forms when carbon -14 decays?

Solution 1 What forms when carbon -14 decays? 14C  0  + 14 N 6 -1 7 6 -1 7 Worksheet: Balancing nuclear equations

Half-Life of a Radioisotope The time for the radiation level to fall (decay) to one-half its initial value decay curve 8 mg 4 mg 2 mg 1 mg initial 1 half-life 2 3

http://www.eas.asu.edu/~holbert/eee460/decay.html

Examples of Half-Life Isotope Half life C-15 2.4 sec Ra-224 3.6 days I-125 60 days C-14 5700 years U-235 710 000 000 years

HALF- LIFE

Learning Check 2 ½ life amount time How many half lives will it take for 50 grams of 99 Tc to decay to 6.25 g? ½ life amount time

Solution 2 How many half lives will it take for 50 grams of 99 Tc to decay to 6.25 g? 3 half lives ½ life amount time 0 50 0 1 25 2.13 x 105 2 12.5 2 (2.13 x 105) 3 6.25 3 (2.13 x 105)

½ life amount time

Transmutation Natural Artificial One element becomes another. Alpha Beta Gamma Positron Artificial Fission Fusion

Nuclear Fission Fission larger unstable nuclei break up into smaller more stable nuclei; release of neutrons causes a chain reaction and energy release 235U + 1n 139Ba + 94Kr + 3 1n + 92 0 56 36 0 Energy

Fission

Nuclear Power Fission Reactors Cooling Tower

Nuclear Power Fission Reactors

Nuclear Fusion Fusion small nuclei combine 2H + 3H 4He + 1n + 1 1 2 0 1 1 2 0 Occurs in the sun and other stars, hydrogen bomb Energy

Nuclear Power Fusion Reactors (not yet sustainable)

Nuclear Power Fusion Reactors (not yet sustainable) National Spherical Torus Experiment Tokamak Fusion Test Reactor Princeton University

Fission vs. Fusion 235U is limited fuel is abundant danger of meltdown toxic waste thermal pollution fuel is abundant no danger of meltdown no toxic waste not yet sustainable

Nuclear Weapons Atomic Bomb chemical explosion is used to form a critical mass of 235U or 239Pu fission develops into an uncontrolled chain reaction Hydrogen Bomb chemical explosion  fission  fusion fusion increases the fission rate more powerful than the atomic bomb

Learning Check 3 Indicate if each of the following are Fission (2) fusion Nucleus splits Large amounts of energy released Small nuclei form larger nuclei Hydrogen nuclei react Energy

Solution 3 Indicate if each of the following are Fission (2) fusion 1 Nucleus splits 1 + 2 Large amounts of energy released 2 Small nuclei form larger nuclei 2 Hydrogen nuclei react

Nuclear Chemistry Uses Dating dating previously living materials (Carbon-14) dating rocks and other geological formations (Uranium-238)

Nuclear Chemistry Uses Radiation treatment using -rays from cobalt-60. Medical Application Radiation Treatment larger doses are used to kill cancerous cells in targeted organs (Cobalt-60) Radioisotope Tracers (absorbed by specific organs and used to diagnose diseases) Iodine-131 detection and treatment of thyroid conditions Technetium-99 detects presence of tumors

Nuclear Chemistry Uses Food Irradiation  radiation is used to kill bacteria (Co-60 and Cs-137) Consumer Products ionizing smoke detectors - 241Am

Nuclear Chemistry Uses Radioactive Tracers (tracers follow the path of a material in a system) Map the path of carbon in metabolic processes (Carbon-14) study plant growth, photosynthesis (Phosphorus-31)

Nuclear power plant.

Diagram for the tentative plan for deep underground isolation of nuclear waste.