Warm-up What do you know about Radioactivity? Make a list of facts….

A is for Atom

Ch Nuclear Radiation

Most influential research by Marie Curie Nobel Prize in Physics 1903 and again in 1911

Chemical vs Nuclear Reactions Chemical reactions rearrange electrons Elements stay the same and are recombined Energy released: low to high (dynamite Rx) _______________________________________ Nuclear reactions rearrange p+, n o New elements are formed Radiation is a product Forces: extreme (nuclear explosion, A, H-bombs)

Radioisotopes All elements until AN 83 (Bi) are stable (few exceptions like C-14 or H-3) And all elements with AN >83 are radioisopes Examples: Uranium, Radium, Plutonium, Neptunium, Thorium, Protactinium ….

3 Types of Radiation All nuclear radiation can potentially be dangerous to organism ranging from moderate to very damaging Alpha radiation Beta radiationincreasing danger Gamma radiation

Penetrating Power of Radiation

Protection from Radiation Alpha: sheet of paper, clothes Beta: wood panel, aluminum foil Gamma: several cm of lead or several m of concrete can partially block gamma rays

Alpha ( α) Radiation is caused by Alpha-Particle particle written as 4 2 He - α particle it’s a Helium nucleus w/o e- it’s the particle beam Rutherford used in his gold foil experiment

Alpha Decay

Writing Alpha Decay Rx U _?_ He Law of Conservation of Mass!!! Atomic number of new element is lower by 2!!!

Practice Show the alpha decay of Neptunium-195

Beta ( β) Radiation A beta particle is a fast-moving electron Created when a neutron breaks apart neutron → proton + electron (β –particle) Beta particle o -1 e

Beta Decay

Writing Beta Decay Rx U β _?_ + o -1 e Increases atomic number of new element by 1!!!

Practice: write beta decay of Neptunium-201

Gamma Radiation Gamma rays are no particles but electromagnetic radiation like light-, UV- or radiowaves high energy photons Cannot be written in form of a Rx Radioactive decay often produces alpha, beta and gamma radiation simultaneously!!!

Electromagnetic Spectrum

25.2 Half-Life of Radioisotopes total # of isotopes in PT: 1500 radioisotopes: 260 Half-Life t 1/2 :time it takes for half of the isotope to decay and form a new element

Half-Life Curve

Concentration of old and new elements

Examples Radioisotope Half-life Bismuth sec Sodium hours Iodine days Hydrogen years Cobalt years Carbon years Uranium billion years

Practice Sodium-24 beta decays. What new isotope is formed when it decays? How much new isotope is formed after 45 hours? How much old isotope is left after 45 hours? How much C-14 is left after 11,400 years? How much old isotope is left after 5 half lives?

Warm-up Create a Venn Diagram that contrasts regular isotopes and radioisotopes

Journal 1.How much old isotope is present after 5 half lives in % and in fraction 2.How much new isotope is present? 3.Which isotopes from your list would you choose for fossils that are 500 years 5000 years 1 billion years

Ch Radiation in Your Life

Nuclear Fission Fission = splitting (of a nucleus) creates a chain reaction of high speed neutrons that split more nuclei generates enormous amounts of energy

2 Types of Fission uncontrolled nuclear reaction – A Bomb controlled nuclear reaction – nuclear power plant

Controlled Nuclear Fission Speed of the neutrons is lowered by graphite rods The coolant is heated that power steam turbines to generate electricity

Nuclear Reactor

How does a Nuclear PP works NPP san onofre

+/- of Nuclear Energy -Forever storage of nuclear waste -Accidents that can lead to widespread contaminations (Three Mile Island, Chernobyl, Fukoshima) + no pollution, greenhouse gas emission (CO2) + independence from oil (political costs…) + long term, large scale, reliable energy production

Nuclear Fusion Fusion: combining (two small nuclei) more energy than nuclear fission Also creates a chain reaction Sun does nuclear fusion

Nuclear Fusion life nf

Forces Within the Nucleus Electromagnetic repulsion: Protons repelling each other Nuclear forces: neutrons and nuclear binding energy glue protons together “cosmic glue” Nuclear forces > electromagnetic repulsion, element is stable Nuclear forces < electromagnetic repulsion, radioisotope

25.4 Radiation in your life

Ionizing Radiation Radiation with enough energy to knock electrons of the exposed elements and change them Formation of ions – charged atoms (#p+ and e- is not equal!!!) Particle radiation: alpha and beta particles Electromagnetic waves: UV, X-rays, gamma rays

Electromagnetic Spectrum

DNA Damage from Radiation

Dose vs Damage - radiation doses are measured in Sieverts

radiation cellphones and tumors

Nuclear Medicine Radiation treatment of cancer. Radiation affects quickly dividing cells more than non- dividing cells (normal) Injection of Iodine-131 for the detection of thyroid function

Research Radiolabeling of molecules, cell parts with radioisotopes H-3, S-35…

Fossil dating When the animal is alive it incorporates radioactive trace elements from environment Example: C-14 alongside C-13, C-12 T 1/2 = 5700 years When animal dies/fossilizes C-14 is not replaced but undergoes transmutation to N-14. What type of transmutation turns C-14 into N- 14? The older the fossil the more C-14 is gone