Name Date Due Atomic Structure and the Periodic Table: Unit Objective Study Guide—Part 1 Directions: Write your answers to the following questions in the space provided. For problem solving, all of the work leading up to the final answer must be shown in order to receive credit. You will receive no credit for ―magic answers‖. 1. Define atom. Atom – the smallest particle of an element that retains all the properties of that element 2. Distinguish between protons, electrons, and neutrons in terms of their relative masses and charges. Complete the following table. Subatomic Particle Symbol Mass (amu) Charge Proton p+ 1 amu positive Electron e- 1/1836 negative Neutron n° 1amu amu neutral 3. Discuss the structure of an atom including the location of the proton, electron, and neutron with respect to the nucleus. Which subatomic particle(s) is/are located in the nucleus? protons and neutrons Which subatomic particle(s) is/are located outside the nucleus? electrons 4. Define atomic mass unit. What is an atomic mass unit? a unit of mass equal to one-twelfth the mass of a car What element is an atomic mass unit based upon? Carbon - 12 1 5. Define atomic number and determine the atomic number for given elements (isotopes). Atomic number – the number of protons in an atom 6. Define mass number and determine the mass number of an element (isotope) given the appropriate information. Mass number – the sum of the protons and neutrons in an atom Is the mass number of most elements listed on our periodic tables? No, the atomic mass is given and not the mass number. 7. Use the atomic number and mass number of an element to find the number of protons, electrons, and neutrons. Complete the following table: Element Nuclear Atomic Mass Number Number of Number of (hyphen notation) Symbol Number Number of Protons Neutrons Electrons 3 hydrogen-3 1H 1 3 1 2 1 80 Selenium- 34Se 34 80 34 46 34 108 Silver80- 108 47Ag 47 108 47 61 47 40 Calcium- 20Ca 20 40 20 20 20 27 Aluminum40 - 13Al 13 27 13 14 13 27 2 8. Define isotopes and describe how the isotopes of an element differ. What are isotopes? Atoms of the same element with ber of pons but different number of neutrons What are three differences between isotopes of the same element? mass number, number of neutrons, and atomic mass of each isotope Which of the following represent isotopes of the same element? Explain your answer. 14 14 12 13 6X, 7X, 6X, 7X 1st and 3rd, 2nd and 4th. They have the same number of protons (bottom number). Explain why isotopes of the same element have the same chemical behavior. They have the same number of electrons. 9. Use the concept of isotopes to explain why the atomic masses of elements are not whole numbers. The atomic mass for an element is given on the periodic table. What is the atomic mass of an element? The atomic mass is the weighted average of the masses of the isotopes of an element. What information is needed in order to calculate the atomic mass of an element? Percent abundance and mass of each isotope as they 10. Calculate the average atomic mass of an element from isotope data. Three isotopes of argon occur in nature – Argon-36, Argon-38, and Argon-40. Calculate the average atomic mass of argon to two decimal places, given the following relative atomic masses and abundances of each of the isotopes: argon-36 (35.87 amu; 0.337%), argon-38 (37.96 amu; 0.063%), and argon-40 (39.96 amu, 99.600%). 0.337 0.063 35.87 amu × = 0.12 amu 37.96 amu × = 0.02 amu 100 100 99.600 39.96 amu × = 39.80 amu 0.12 amu + 0.02 amu + 39.80 amu = 39.94 amu 100 3 11. Calculate the percent abundance of an isotope from isotope data. Naturally occurring boron exists as boron-10 and boron-11. Boron-10 has an atomic mass of 10.01 amu. Boron-11 has an atomic mass of 11.01 amu. The average atomic mass of boron is 10.81 amu. a. Which isotope of boron is the most abundant in nature? Explain your answer. Boron-11 is the most abundant in nature. The average atomic mass is closest to the mass of boron-11. b. Calculate the percent abundance of each isotope of boron. 10.81 amu = 10.01 amu 푥 + 11.01 amu (1 − 푥) Boron -10 = 19.8% 10.81 amu = 10.01 amu 푥 + 11.01 amu − 11.01 amu (푥) 10.81 amu − 11.01 amu = 10.01 amu 푥 − 11.01 amu (푥) Boron-11 = 80.2% −0.20 amu = −1.01 amu (푥) −0.20 amu 푥 = boron − 10 = 0.198 = 19.8% −1.01 amu 1 − 푥 = boron − 11 = 1 − 0.198 = 0.802 = 80.2% 12. Define radioactivity, radiation, radioisotopes, and radioactive decay. Radioactivity – the process by which unstable atomic nuclei achieve stability Radiation – the penetrating rays (gamma) and particles (alpha and beta) emitted by a radioactive source Radioisotopes – Isotopes of atoms that have unstable nuclei and emit radiation to attain more stable atomic configurations Radioactive decay – A spontaneous process in which unstable nuclei lose energy by emitting radiation 4 13. Describe how the stability of a nucleus is determined and predict whether or not certain isotopes would be stable or not. Explain how you can predict whether or not an isotope is likely to be stable if you know the number of neutrons and protons in the nucleus. The band of stability can be used to predict whether or not an isotope is likely to be stable. Plotting the below the band of stability will spontaneously decay. Use the band of stability to determine whether carbon-14, neon-20, zirconium-90 and neodymium-130 have nuclei that are stable. 14. Compare the penetrating ability and shielding requirements of alpha particles, beta particles, and gamma rays. Which form of radiation (alpha, beta, or gamma) has the highest relative penetrating power? gamma lowest penetrating power? alpha When you have an x-ray done of your teeth at the dentist’s office, you must wear a lead apron. Why? The lead apron is to protect you from gamma Which form of radiation can be blocked by paper? alpha Which form of radiation can be blocked by metal foil? beta 5 15. Describe the different types of radioactive decay and their effects on the nucleus. Complete the following table. Change in Change in Change in Process Symbol mass number atomic number neutron/proton ratio 4 α – particle production 2He -4 -2 increases 0 β – particle production −1푒 none +1 decreases 0 Positron production +1푒 none -1 increases 0 Electron capture −1푒 none -1 increases 0 γ – ray production 0훾 none none no change 16. Explain, write, and balance nuclear equations. a. Write a balanced nuclear equation for the alpha decay of americium-241. 241 4 237 95Am → 2He + 93Np b. Write a balanced nuclear equation for the beta decay of bromine-84. 84 0 84 35Br → −1e + 36Kr c. Write the balanced nuclear equation for the alpha particle bombardment of plutonium- 239. The reaction products include a hydrogen atom and two neutrons. (Identify the other product.) 239 4 1 1 240 94Pu + 2He → 1H + 20n + 95Am d. Write a balanced nuclear equation for the reaction in which oxygen-15 undergoes positron emission. 15 0 15 8O → +1e + 7N e. Complete the following nuclear equation. What type of nuclear process does the equation represent? 142 142 61Pm + ? → 60Nd 142 0 142 61Pm + −1e → 60Nd , electron capture 6 17. Use a decay series to write the decay mode for transuranium elements. Write the series of reactions that represent the decay mode of radium-226 to lead-208. 18. Define half-life and calculate the half-life of certain isotopes. Half-Life – the time required for one-half of a radioisotope’s nuclei to decay into its products. A sample initially contains 50.0 g of cobalt-60. After 24 years, only 6.25 g of the sample remain. What is the half-life of cobalt-60? 7 19. Use half-life information to determine the amount of a radioisotope remaining at a given time. A patient is administered 20 mg of iodine-131. How much of the isotope will remain in the body after 40 days if the half-life of iodine-131 is 8 days 1 2 3 4 20 mg → 10 mg → 5 mg → 2.5 mg → 1.25 \ Graph the following data for the radioactive decay of strontium-90. Graph mass remaining as the dependent variable and time as the independent variable. Half -Life of Time (years) Mass Remaining (g) 0 100.0 Strontium -90 10 78.0 20 61.0 30 47.6 40 37.1 50 28.9 60 22.7 a. Estimate the half-life of strontium-90. Approximate ly 29 years. b. Estimate the amount of the original sample of strontium-90 that would remain after 35 years. 20. Differentiate between nuclear fission and nuclear fusion. Compare and contrast nuclear fission and nuclear fusion reactions in terms of the particles involved, amount of energy produced, and the changes they undergo. Describe some of the problems of using fission as a power source. Describe some of the current limitations of fusion as a power source. n able to 8 .