Nonrenewable Energy: Nuclear Energy Part 2
What do you know about Nuclear Chemistry? http://ed.ted.com/lessons/radioactivity-expect-the-unexpected-steveweatherall
I. Radiation Radiation = any movement of energy through space Example: electromagnetic radiation Not all radiation is dangerous! o How powerful or dangerous radiation is depends on two factors: the wavelength and the energy The the shorter, wavelength the higher the energy The higher the, energy the more stuff it can pass through = the most dangerous! Example: X-rays and have Gamma rays the most energy so most dangerous
Radiation can be categorized into two groups: nonionizing or ionizing Nonionizing Lower energy radiation: radio, microwave, infrared, visible light, some UV rays Causes molecules to vibrate faster or give off light Ionizing Higher energy radiation: some UV rays, X-Ray, Gamma Causes electrons to leave atoms and molecules, creating ions Gamma rays can even break up an atom s nucleus Therefore, ionizing radiation is more dangerous
II. What is Nuclear Chemistry? Nuclear Chemistry = The study of reactions that are caused by a of change in the nucleus an atom Unlike regular chemical reactions where elements simply re-arrange, in nuclear reactions new are elements! formed o Protons in nucleus change = different element When a nucleus break ups it releases a lot of energy and that energy is what is used in nuclear energy sources o Recall: nuclear energy is a nonrenewableenergy source While nuclear energy does use elements that can be found in nature, the element most commonly used in a nuclear power plant (uranium- 235) is very rare and there is a limited amount of it
Fill in each circle with one of the following: New element Ion Isotope Molecule/compound
Why does this happen? Why does the nucleus of an atom change? It comes down to stability. Some isotopes of elements are stable, some are unstable o Nuclear Stability= the larger (more massive) a nucleus is, the harder it is for it to stay together When isotopes are, unstable they emit energy in the form of radiation = they are radioactive When a nucleus is radioactive, it gives off decay particles and in changes from one element to another order. to become more stable This process is known as. natural decay or transmutation
III. Modes of Decay Radioactivity (radioactive decay)= the decay or break-up of the nucleus of an unstable atom in order to become more stable o Results in the emission or release of particles and/or energy There are different modes or types of decay different particles that are released Modes of Decay (See Table ) O
Type of Decay Symbol Charge Mass Penetration Strength α alpha 4 2 He or 4 2 α +2 4 low β - Beta 0 1 e or 0 1 β -1 0 (very little) moderate β + Positron 0 +1 e or 0 +1 β +1 0 (very little) moderate γ Gamma Rays 0 0 γ 0 0 (light energy) high
Penetration Strength= How far into a material the radioactive particle will go o The smaller the particle (less mass), the more it can penetrate o The more a particle can penetrate, the it more dangerous is What is the most dangerous particle? gamma rays
IV. Types of Transmutations Transmutation = when a nucleus decays and changes into a new and different nucleus (aka radioactive decay) 1. Natural Transmutation= when an unstable nucleus spontaneously breaks up and releases particles and/or energy in order to become more stable o Table N is a list of isotopes that undergo natural transmutation Shows what type of particles they release (aka decay mode) and their half-lives (how long it takes to decay)
Check for Understanding Table N contains a list of some of the more common radioisotopes, their half-lives, their symbols, and their names. NUCLIDE = an ISOTOPE of a given element 1. Which of the following pairs of nuclides has the same type of radioactive decay mode? a. K-37 and K-42 b. Fr-220 and Th-232 c. Ne-19 and P-32 d. U-232 and U-235 2. Which of the following radioisotopes will take the longest to decay from 100 g to 50 g? a. Fe-53 b. Pu-239 c. Th-232 d. N-16
3. Which of the radioisotopes listed below emits a decay product with a positive charge? a. Ra-226 b. Au-198 c. H-3 d. Sr-90 4. Which of the radioisotopes listed below emits a decay product with the greatest mass? a. Co-60 b. C-14 c. Ca-37 d. Fr-220
2. Artificial Transmutation= when a stable nucleus gets bombarded or hit by another particle, producing new elements o man-made reaction doesn t happen naturally
V. Nuclear Equations Summary of Types of Reactions A. Physical Reaction: H 2 O (s) H 2 O (l) Same? Compound and mass (and charge) Different? Phases (s l) B. Chemical Reaction: 2H 2 (g) + O 2 (g) 2H 2 O (l) Same? Mass and # of atoms (and charge) Different? compounds C. Nuclear Reaction: 16 7N 0-1e + 16 8O Same? Mass and charge Different? elements
As mentioned before, there are two types of decay: natural and artificial 1. Natural Decay - because the process is spontaneous, natural radioactivity equations always have forming one reactant two products o Use Table N to identify the type of decay for specific nuclide o Use Table O to identify notation of decay mode Examples: 1. Francium 220 2. Gold 198 3. Neon 19
4. Iodine 131 5. Uranium 233 6. Potassium 37 How do you balance nuclear equations? Sum of charges and mass numbers are equal on both sides
2. Artificial Decay - because artificial transmutation involves a stable nucleus being forced to change, the equation always involves two reactants forming new products Examples: 4 2 He 1. 9 4 Be + 12 6 C + 1 0 n 30 15 P 2. 27 13Al + 4 2 He 1 0 n + Natural Decay Common to Both Artificial Decay Unstable nucleus decays by itself ( ) spontaneous Mass and charge conserved Both form new Stable nucleus has to get hit to decay 1 reactant elements 2 reactants Produces less energy Both produce energy Produces more energy
1. Given the reaction: Check for Understanding Which particle is represented by X? 1. 2. 3. 4.
2. Which equation represents a spontaneous transmutation? 1. Ca(s) + 2H 2 O(l) Ca(OH) 2 (aq) + H 2 (g) 2. 2KClO 3 (s) 2KCl(s) + 3O 2 (g) 3. 4.
VI. Fission and Fusion Fission = splitting of a large nucleus into smaller nuclei o releases neutrons and large amount of energy o Uranium-235 and plutonium-239 are most commonly used Example: Fission of Uranium-235 (ANIMATION) 235 92 U + 1 0n 92 36Kr + 141 56Ba + 3 1 0n + ENERGY
Fusion = combining nuclei (or fusing) of smaller to produce a larger one (greater mass) o Creates more energy than fission o Hydrogen-1 is most commonly used in fusion reactions Example: Fusion of Hydrogen nuclei 3 1 H + 2 1H 4 2He + 1 0n + ENERGY
Nuclear Fission Common to Both Nuclear Fusion Splits larger nucleus into smaller particles Used to produce electricity in power plants Produces radioactive waste Both generate energy the same way (Convert mass ) energy Less energy more energy combines two small nuclei together to form a larger one Used by! the sun Produces essentially no radioactive waste
VII. Half-Life Half-Life = time it takes for half of the original sample of radioactive nuclei to decay o During one half-life, half of the radioactive nuclei break down and change into new, more stable nuclei o With each additional half-life, the sample keeps cutting in half, but - never fully reaches zero all the radioactive nuclei never fully change into stable nuclei https://www.explorelearning.com/index.cfm?method=cresource.dspdetail&resourceid=369 The shorter the half-life, the less time an unstable isotope is emitting radiation before it decays into something more stable and less dangerous The half-life of many radioactive isotopes can be found on Table N Equation: total time passed half life = # of half-lives
Examples: 1. 131 I is a radioactive substance used to detect and treat thyroid cancer. What mass of I-131 remains 24 days after a 2 microgram sample is administered to a patient? 2. Radon-222 is a carcinogenic house pollutant. How much time must elapse before 20 grams of radon-222 decays, leaving only 1.25 grams of the original isotope?
3. Based on Reference Table N, what fraction of a radioactive 42 K sample would remain unchanged after 24.7 hours? 4. Based on the graph below, what is the half-life of this substance? 5. What fraction of a sample of cobalt-60 remains radioactive after 3 half-lives?
VIII. Uses and Dangers of Nuclear Chemistry Uses/benefits Dating: Certain radioisotopes with longer half-lives can be used to trace the age of substances using their half-life Examples: o Carbon 14 (C-14) can be used to trace the age of any living thing (people, plants, animals) because all living things contain carbon o Uranium can be used to trace the age of the Earth since uranium is a natural part of some rocks and has an extremely long half-life Medical: Certain radioisotopes with shorter half-lives can be used for medical reasons shorter half-life means they quickly decay into something stable before they cause harm to the body Examples: o Iodine 131 used to detect and treat thyroid cancer o Cobalt 60 emits gamma rays that can destroy cancer o Technetium 99 detects cancerous tumors
Dangers/Risks Large amounts of radiation given off by isotopes can cause environmental damage and serious illnesses The isotopes used in nuclear power plants produce waste products that have long half-lives so they remain radioactive for long periods of time, making them difficult to store and dispose of o accidents can also release harmful radioactive waste into air and water Chernobyl, Ukraine (1986) (news report)