* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download The Band of Stability
Survey
Document related concepts
Nuclear fission wikipedia , lookup
Gamma spectroscopy wikipedia , lookup
Nuclear and radiation accidents and incidents wikipedia , lookup
Nuclear fission product wikipedia , lookup
Fallout shelter wikipedia , lookup
Ionizing radiation wikipedia , lookup
Background radiation wikipedia , lookup
Isotopic labeling wikipedia , lookup
Nuclear binding energy wikipedia , lookup
Technetium-99m wikipedia , lookup
Radioactive decay wikipedia , lookup
Valley of stability wikipedia , lookup
Transcript
Name: _____________________________ Date: ______________________________ Class: ______________________________ Nuclear Chemistry Chemistry Honors The Band of Stability Introduction: Radioactivity is the spontaneous emission of radiation by nuclei. Radioactive decay changes the nature and identity of an atom’s nucleus. This occurs for a specific reason. Elements from hydrogen to lead (atomic numbers 1-82) have stable isotopes in which the tendency of protons to repel one another is overcome by attractive nuclear forces. The forces require ideal distances between the protons. The neutrons help create these ideal distances. If there are too many or too few neutrons, the nucleus becomes unstable. If an atom has more than 82 protons in the nucleus, there is no arrangement of neutrons that can produce more than attractive forces than repulsive forces. Therefore, all isotopes of elements beyond lead are radioactive. Their only route to stability is to first reduce the overall size of the nucleus by losing large particles. Part I: Create a Band of Stability You will be graphing the proton and neutron numbers for some isotopes that are known to be stable. - Using an entire side of a piece of graph paper, draw a vertical “y” axis and label it “Neutrons.” Draw a horizontal “x” axis and label it “Protons.” Scale the y-axis so that it goes from 0 to 150. Scale the x-axis so that it goes from 0 to 100. On a piece of loose leaf, complete the following table. ** Remember! This is only a small portion of the list of stable isotopes. - Plot the points from the table that correspond to the axes on your graph. Draw a bold, smooth curve through the points. (As smooth as possible.) Part II: Unstable Isotopes - On a piece of loose leaf, complete the following table. ** Remember! This is only a very small portion of the list of unstable isotopes. - Plot the points from the table that correspond to the axes on your graph. Label each point with the identity of the isotope that it represents. **Elements that fall outside of the band of stability cannot exist long enough to be recognized as elements. ** The elements that are found in the middle of the band of stability have a very stable nucleus. Name: _____________________________ Date: ______________________________ Class: ______________________________ Chemistry Honors Nuclear Chemistry Transmutations Part III: Transmutations Now that you have learned about the band of stability and what it means, you are ready to learn about the different types of radioactive decay. Go to the following video and fill in the answers below. The video is about 10 minutes long. https://www.youtube.com/watch?v=KWAsz59F8gA 1. A transmutation occurs when an atom ______________________________________________ ______________________________________________________________________________ ______________________________________________________________________________. 2. Transmutations occur because atoms need to be __________________________. 3. What causes an atom to be unstable? 4. An atom of radium (Ra) becoming an atom of radon (Rn) is an example of ______________________________ or _________________________________. 5. The half-life of an element is _______________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________. Example 1: Polonium-214 has a relatively short half-life of 164 seconds. How many seconds woul it take for 8.0 g of this isotope to decay to 0.25 g? Example 2: By approximately what factor would the mass of a sample of copper-66 decrease in 51 minutes? The half-life of copper-66 is 5.10 min. Common Types of Radioactive Decay 1. Alpha Decay Can be described by: - The nucleus of an atom splits into two parts The alpha particle is emitted from the nucleus The nucleus that is left behind now has an atomic number reduced by 2 and its mass number reduced by 4. (2 protons and 2 neutrons were emitted Write the symbol for an alpha particle using isotopic notation in the space below. Here is a typical alpha decay equation: Fill in the blank space below. 222 88𝑅𝑎 → + 218 86𝑅𝑛 - Alpha radiation can be blocked by _________________________________________________ ______________________________________________________________________________. 2. Beta Decay Can be described by: - The emission of an ____________________. Write the symbol for the particle here - The atomic number goes up by one and the mass number remains unchanged. A neutron inside the nucleus of an atom breaks down into a ___________________ and an ___________________ which is emitted. Here is a typical beta decay equation: Fill in the blank space below. 14 6𝐶 → + 147𝑁 ** Beta particles have less charge than alpha particles and much less mas. Consequently, beta particles are more penetrating! While they cannot be stopped by a piece of paper they can be stopped by _____________________________ or ______________________________. 3. Gamma Radiation Can be described by: - - The emission of _____________________ only. Gamma ray- a high energy photon emitted by a radioisotope; nuclei can emit gamma rays by themselves, or the emission of energy can accompany the emission of an alpha or beta particle. Can the emission of a gamma ray change the atomic number or mass number of an element? Write the symbol for gamma radiation here ** Gamma rays are extremely high energy and can be very dangerous! - This energy can be released as o o o o NOTE: The terms alpha, beta, and gamma radiation may also appear as alpha, beta, and gamma decay. Additional Nuclear Reactions You will also be responsible for knowing the following nuclear reactions. 4. Positron Decay Positron decay is the mirror image of beta decay and can be described by: - The emission of a positron (a particle with the mas of an electron but a positive charge). Something inside the nucleus breaking down causing a proton to become a neutron. The atomic number goes down by one and the mass number remains unchanged. - 0 The symbol for a positron is: +1 𝑒 Here is a typical positron decay equation 23 12𝑀𝑔 → 23 11𝑁𝑎 + +10𝑒 5. Electron Capture Can be described as: - An electron from the closest energy level falls into the nucleus, which causes a proton to become a neutron. - The atomic number goes ___________ by one and the _____________ ______________ remains unchanged. Here is a typical electron capture equation: 81 36𝐾𝑟 + 0 −1𝑒 → 81 35𝐵𝑟 What is the distinct difference between electron capture and the other types of radiation? Practice 1. Classify each of the following nuclear reactions by particle and type of radiation (decay or capture). e.g. alpha decay a. 13 7𝑁 b. 238 90𝑇ℎ → c. 238 90𝑇ℎ → 42𝐻𝑒 + 234 88𝑅𝑎 d. 238 90𝑇ℎ + → 0 −1𝑒 + 138𝑂 0 +1𝑒 0 −1𝑒 + 238 89𝐴𝑐 _______________________________________ _______________________________________ _______________________________________ → 𝛾 + 238 89𝐴𝑐 _______________________________________ Name:___________________________ Chemistry Honors Date:__________________Period:____ Nuclear Decay Worksheet 1. Using the figure to the right, write the reaction equations represented by letters A, B, and C. This figures shows the decays that uranium-238 undergoes to become lead-206. A: _________________________________________ B: _________________________________________ C: _________________________________________ 2. Nuclear decay takes time. This time is measured in half lives. Explain the concept of a half life. 3. An isotope of cesium (cesium-137) has a half-life of 30 years. If 1.0 mg of cesium-137 disintegrates over a period of 90 years, how many mg of cesium-137 would remain? 4. In 5.49 seconds, 1.20 g of argon-35 decay to leave only 0.15 g. What is the half-life of argon-35? 5. Selenium-83 has a half-life of 25.0 minutes. How many minutes would it take for a 10.0 mg sample to decay and have only 1.25 mg of it remain? How many half-lives is this? Nuclear Equations Part I: Complete the nuclear reaction equations below. Then classify them by particle and type (decay or capture). 1. 212 84𝑃𝑜 → 42𝐻𝑒 + _______ 2. 142 61𝑃𝑚 3. 218 84𝑃𝑜 + _______ → → 0 −1𝛽 142 60𝑁𝑑 + _______ 4. 74𝐵 → _______ + 73𝐿𝑖 classify: __________________________ classify: __________________________ classify: __________________________ classify: __________________________ 5. 22 11𝑁𝑎 6. 238 92𝑈 → _______ + ______ + _______ alpha and gamma decay classify: __________________________ 7. 37 18𝐴𝑟 + ______ →→ _______ classify: __________________________ + _______ → 22 10𝑁𝑒 classify: __________________________ Part II: 1. Write the nuclear equation for the release of a beta particle by lead-210. 2. Write the nuclear equation for the positron decay by thorium-232. 3. Write the nuclear equation for the gamma decay of cerium-144.