2What do you think of when you hear Nuclear Chemistry?
3History Henri Becquerel (1852-1908) Originally thought sunlight caused uranium to radiateDiscovered the spontaneous radiation while waiting for a sunny day to test his theoryMarie Curie ( ) and her husband Pierre Curie ( )Worked w/ BecquerelEventually showed that the rays were from uranium atomsCame up with the term “radioactivity” to describeHistory
4Why Radioactive? Some isotopes are stable and others are not. Nucleus is protons and neutronsProtons are positive so they repelNeutrons are only stable when near a protonSome have:Too many protonsToo many neutronsJust plain too manySo they “fall apart”Why Radioactive?
15How does this help? Chart helps predict type of decay Too many neutrons?Emit a beta particle to change a neutron to a proton and move closer to the band of stabilityJust too big?Emit an alpha particle to reduce size of nucleusThere are many types of decay, but chart helps give us targets when trying to manipulate elements to do what we wantHow does this help?
16Writing and Balancing Nuclear Equations Mass numbers and charges are conserved (equal on both sides)Example Alpha Decay𝑃𝑢 → 𝑍 𝐴 𝑋 𝐻𝑒Mass number of product A= ?Atomic Number of product Z= ?Reaction Product X = ?238= A+494=Z+2So… 𝑈 is the answerWriting and Balancing Nuclear Equations
17Writing and Balancing Nuclear Equations Mass numbers and charges are conserved (equal on both sides)Example Beta Decay𝑃𝑢 → 𝑍 𝐴 𝑋 + 𝑒 − ( −1 0 𝛽 )Mass number of product A= ?Atomic Number of product Z= ?Reaction Product X = ?since beta decay is the break up of a neutron into a proton and an electron the mass # doesn’t changeZ will be one greater Z= 95So… 𝐴𝑚 is the answerWriting and Balancing Nuclear Equations
18Practice Show the products of Bismuth -212 undergoing an alpha decay 𝐵𝑖 → 2 4 𝐻𝑒 𝑇𝑙Now the Daughter thallium undergoes a beta decay𝑇𝑙 → 𝑒 − ( −1 0 𝛽 ) 𝑃𝑏Practice
19Half-Life is the time required for half of the atoms in a radioactive sample to decay Number of half-livesElapsed timeAmount of strontium-90 present0 y10.0g129 y5.00g258 y2.50g387 y1.25g4116 y0.625gHalf -Life
20PracticeBandages can be sterilized by exposure to gamma radiation from colbalt-60, which has a half-life of 5.27 years. How much of a 10.0 mg sample of cobalt-60 is left after one half-life? Two half-lives? Three half- lives? How many years is 3 half-lives?5.00mg; 2.50mg; 1.25mg; 15.81yHalf-Life