Nuclear Chemistry Nuclear Reactions involve an atom’s nucleus !!!!

Radioactive Decay Spontaneous breakdown of an atom’s nucleus Breakdown results in a lighter nucleus Emits electromagnetic radiation Nuclear radiation—radiation emitted from nucleus Radioactive nuclide– nucleus that goes through radioactive decay, unstable. (Ex. Uranium Ask where are our nuclear power plants in NC? Nucleii beyond 83—unstable, radioactive

Types of Radioactive Decay Alpha particle (α) Consists of 2 protons, 2 neutrons emitted during decay Helium nucleus ( 24He )—how particle represented Can be stopped by paper, low energy Atomic number goes down 2, atomic mass goes down 4. Equation: 84210 Po  82206 Pb + 24 He Beta particle (β) Electron given off during radioactive decay Can be stopped by lead or glass Increase in atomic # Equation: 614 C  714 N + -10 β Gamma Rays Has the most energy, only stopped by lead Ex. X-Rays Alpha particles are heavy—stopped by paper. Beta particles are lighter—more penetrating power Gamma particles—go through anything (ex. X-ray)---have to wear lead apron.

Types of Decay Alpha Beta Gamma Like He Nucleus Low Energy Blocked by paper & skin Fast-moving e- Blocked by Al foil, clothing, wood No mass, no charge Accompanies alpha/beta High energy Mostly blocked by thick Pb & concrete

Half-Life Time period required for half of a radioactive nuclide to decay. Vary depending on the nuclide, unique for each nuclide. Ex. 146C has a half-life of 5715. Therefore, if we have 10g of 146C, in 5715 years we will have 5g.

Exponential From Google images

Decay series

Initial amount of sample Half-Life Time it takes for ½ of a sample to decay. Need 3 out of 4 to solve: **May also need to figure out # of ½ lives** Initial amount of sample Final amount of sample Length of ½ life Total time measured

AE = AO * 0.5 t/t(1/2) Half-Life Equation AE = Substance amount A0 = Initial substance amount t = time elapsed t1/2 = half-life

Example 1: Plutonium-239 has a half life of 24,110 years Example 1: Plutonium-239 has a half life of 24,110 years. We have 100g of this substance. How many grams will we have after 96,440 years? 6.25g

Half-Life Examples 12) Gold-191 has a half life of 12.4 hrs. What mass of this isotope would remain after 49.6 hrs if you started with a 7.50 mg sample?

Half-Life Examples 3) What is the half-life of an isotope of plutonium, if the original sample was 10.0g and after 420 days there was 1.25 grams?

Nuclear Reactions

Nuclear Fission Nuclear reaction where nuclei are SPLIT Nucleus is broken down into a more stable nucleus. HUGE amount of energy is released **Can induce a nuclear chain reaction!!! Neutrons bombard atom, nucleus splits—produces more neutrons that can then attack other atoms—chain reaction! Reaction continues until all nuclei are split. Happens with Uranium 235 **Type of reaction used in nuclear power plants!!!

Chain Reaction

Uranium-235 used HUGE, HUGE, HUGE amount of water is used to cool the reactors !!!!!

Nuclear Fusion Nuclei having a light mass are joined. Combination of light nuclei Creates heavy nucleus Results in larger, stable nucleus. MORE energy released than in nuclear fission !!! Hard to control Initiated by fission reaction (fission bomb) ---- H bomb **Type of reaction happening in the sun and stars. -fuel: hydrogen atom Fission reaction used to start a fusion reaction in H bomb.

Applications to Nuclear Radiation Radioactive Dating Age determination of artifact based on presence of radioactive nuclide Medical Purposes Cancer treatments Radioactive tracers Food Processing Meat exposed to radiation Kills microorganisms