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PA Problem Set 2a Chapters 4 and 25 The Structure of the Atom and Nuclear Chemistry Due Tuesday October 5th Your work is to be done on separate sheets of paper. All of the papers should be stapled together in the upper left hand corner with this question sheet at the back of the packet. Each of your responses should be numbered the same way as it appears on this packet. Do each Conceptual Question. (70% of grade based upon correct answers) Try the practice questions until you get the hang of them.(0%) answers on the back Try each extension question (30% for trying them) Pen or pencil is acceptable. Please no red pens, I’ll / we’ll use those for corrections Work together… but don’t copy each other. Copying doesn’t help you learn the material Start early… end early… figure out what you already know as soon as you can, and figure out what you need to know as soon as you can. You should read chapters 4 and 25 as we progress through this unit. Chapter 4 The Structure of the Atom Chapter 25 Nuclear Chemistry 4-1 Early Theories of Matter 4-2 Subatomic Particles 4-3 How Atoms Differ 4-4 Radioactive Decay 25-1 Nuclear Radiation 25-2 Radioactive Decay 25-3 Transmutation 25-4 Fission and Fusion 25-5 Science and Radiation Section 4-1Early Theories of Matter Conceptual questions 1) What is still correct with Democritus’s Atomic theory? 2) What is wrong with Democritus’s Atomic Theory? 3) What is still correct with Dalton’s Atomic Theory? 4) What is wrong with Dalton’s Atomic Theory? Practice Questions 5) True False Questions – determine if the following statements are true or false according to Democritus’s ideas about atomos. a. b. c. d. Atomos are divisible. Atomos are hard dense spheres Atomos have varying density – they are heterogeneous. Changes in matter are due to the changes in atomos. 6) True False Questions – determine if the following statements are true or false according Dalton’s Atomic Theory a. b. c. d. All matter is made of small particles called atoms. Atoms are divisible. Atoms of the same element are identical Atoms can be separated, combined or rearranged Extension Questions 7) What is a Scanning Tunneling Microscope? Describe what it does and why it is an important tool for scientists. 8) Why is Dalton’s Atomic theory still taught in school, even though it is over 200 years old? Section 4-2: Sub-Atomic Particles and the Nuclear Atom Conceptual Questions 9) The cathode ray tube was used to discover the electron. Re-Draw the diagram from your notes (or page 92) and include what the ray looks like when the + end of a magnet is brought near the ray. 10) What conclusion did Thomson draw about the make up of atoms from his observations of the cathode ray tube? 11) Rutherford used radioactive material to fire positively charged particles at thin sheets of metal. a. What is the name of those particles? b. What is the composition of those particles? 12) Create a diagram of Rutherford’s Gold Foil Experiment. Be sure to include the following details: the alpha particles, the radioactive polonium, the zinc sulfide lining, the gold foil, and these three locations of hits: the most hits, some hits, and only a few hits. 13) What were Rutherford’s two observations from his famous experiment? 14) What were the two conclusions that correspond to the Rutherford’s two observations? Connect each conclusion with the appropriate observation. Practice Questions 15) Who determined that electrons exist? 16) Who determined the mass of an electron? 17) What is the mass of an electron? 18) Who determined that the nucleus of an atom exists? 19) Who determined the charge of nucleus? 20) What is the charge of the nucleus? 21) Who determined that neutrons exist? 22) What is the mass of a proton? 23) What is the mass of a neutron? Extension Questions 24) Draw three historical pictures of an atom if we could take a picture of it…be as detailed as possible a. Dalton’s Perspective b. Thomson and Millikan’s Perspective c. Rutherford and Chadwick’s Perspective 25) Propose a reason for a neutron to be ever so slightly more massive than a proton. Section 4-3 How Atoms Differ Conceptual Questions 26) Define the following terms a. Atomic number b. Isotope c. Average Atomic Mass d. Percent Abundance 27) How are isotopes of the same element alike? 28) How are isotopes of the same element different? 29) What sub-atomic particle(s) identify/(ies) an element? 30) What sub-atomic particle(s) determine(s) the isotope of an element? 31) Use the data below to calculate the average atomic weight for compound X. Then use your periodic table to identify element X. Isotope 1 = 90. 00 %, 39 a.m.u. Isotope 2 = 9.000 %, 40 a.m.u. Isotope 3 = 1.000 %, 41 a.m.u. 32) One of the stable isotopes of tins is tin-119. The atomic number of tin is 50. How many protons, neutrons and electrons are in one atom of this isotope of tin? 33) What is the atomic mass of an isotope of potassium that has 21 neutrons? Practice Questions 34) How many protons in every atom of calcium? 35) How many neutrons in an atom of lithium-7? 36) How many electrons in every atom of magnesium? 37) How many protons, neutrons and electrons are there in an atom of barium-136? 38) Fill in this table for each atom or ion. You may write on the Problem Set… rather than re-draw the table in your responses. Isotope Symbol # p+ #e - #no Atomic Mass Charge Name Number Number 118 Tin - 118 68 0 50 Sn 19 19 18 F -1 40 10 -1 7 -3 9 10 52 128 tellurium - 128 Extension Questions 39) List the steps needed to calculate the average atomic mass if you are given the relative abundance and mass of each isotope known to exist. 40) Nitrogen has two naturally occurring isotopes: nitrogen-14 and nitrogen-15. The average atomic mass of nitrogen is 14.0007 amu. Which isotope is more abundant? Explain. Section 4-4: Radioactive Decay Conceptual Questions 41) State the law of conservation of mass. 42) Why are atoms unstable? 43) How do unstable atoms gain stability? 44) A radioactive element having atomic number 82 and atomic mass 214 loses a beta 0 particle, –1. What is the resulting particle? 45) What type of decay is the reaction below, and what isotope completes this nuclear equation? 27 2 4 Al + H 13 1 2He + ? Practice Questions 46) Complete this chart on the three types of radioactive decay Type Symbol Mass (amu) Alpha Beta Gamma Charge 238 47) If the radioactive atom 92U emits an alpha particle, the atom remaining is represented by (A) 238 92U (B) 236 92Th (C) 234 92U (D) 234 234 90Th (E) 91Pa 48) What term completes this equation? 30 14Si 4 (A)2He 2 1 (B)1H 32 0 + ? 16S + –1e 0 (C)1H (D) –1e 214 49) What particle is emitted when lead–214, 82Pb, undergoes natural radioactive 214 decay to bismuth–214, 83Bi? 4 (A) an alpha particle, 2He (B) a beta particle, –1e 0 1 (C) a proton, 1H (D) a neutron, 0n 1 Extension Question 50) Recently Alexander Valterovich Litvinenko was poisoned by radioactive polonium-210. a. Research who he was and why he was poisoned. b. Find out what polonium-210 does to people. c. Write the nuclear reaction of polonium-210 decaying into lead-206 via an alpha decay. Chapter 25 Nuclear Chemistry Read Chapter 25 After having read through chapter 25, respond to these conceptual questions. 51) Define the following terms: a. critical mass d.fusion g.radioisotope b.decay e. half life c. fission f. transmutation 52) Make (or find) a graphical timeline of the development of modern atomic theory with at least 10 important dates and/or discoveries. After having read through chapter 25, respond to these practice questions. 53) Which type of radiation has a +2 charge? a. Alpha b. beta c. gamma d. neutron 54) Which type of radiation generates the highest energy – is the “hardest” to block? a. Alpha b. beta c. gamma d. neutron 55) Finish the following nuclear reactions. Tell if they are alpha or beta decays. a. b. 238 234 92 90 19 9 U Th + ____ 19 F ___+ 10 Ne c. 222 86 d. 4 Rn ___ + 2He 210 85 0 At ___ +-1 56) What element was the first synthesized by scientists (namely) Ernest Rutherford? 57) How many grams of sample are left after 20 minutes if 100 grams start decaying with a half life of 5 minutes? 58) How long will it take 100 grams of radioactive sample to decay so that only 6.25 grams remain and the samples half life is 3 days? 59) How long is the half life of an isotope if 2.0 grams of sample remain from a 64 gram sample after 30 years? After having read through chapter 25, respond to these extension questions. 60) Element number 96 is named Curium. Do you think Marie and Pierre Curie did enough in the advancement of science to have an element named after them? Explain. 61) Thorium-231 is a radioactive isotope. It decays in ten steps to form lead-207. The ten steps are:. Write this decay series starting with 231Th and progressing to 207Pb. Show each step individually. Answers to Practice Problems 5) a Atomos are divisible.false – atomos are indivisible spheres 5b. Atomos are hard dense spheres true, they are according to Democritus 5c. Atomos have varying density – they are heterogeneous.false- they are homogeneous 5d. Changes in matter are due to the changes in atomos. False –atomos do not change 6a. All matter is made of small particles called atoms. true, it is! 6b. Atoms are divisible. True for Dalton, false for us today, p+, no and e- exist 6c. Atoms of the same element are identical true for Dalton, false for us – isotopes exist 6d. Atoms can be separated, combined or rearranged true – these are reactions 15) Who determined that electrons exist? thomson – cathode rays are electrons 16) Who determined the mass of an electron? Millikan in his oil drop experiement 17) What is the mass of an electron? 9.1 x 10-28 g 18) Who determined that the nucleus of an atom exists? Rutherford and his gold foil 19) Who determined the charge of nucleus? Rutherford and his gold foil 20) What is the charge of the nucleus? Positive 21) Who determined that neutrons exist? Chadwick 22) What is the mass of a proton? 1.67 x 10-24grams 23) What is the mass of a neutron? 1.675 x 10-24 grams 34) How many protons in calcium? Ca’s atomic # is 20, so there are 20 protons 35) How many neutrons in an atom of lithium-7? Li’s atomic # is 3, so there are 3 protons, its mass is 7, so 3 + no = 7 the # of no must be 4. 36) How many electrons in every atom of magnesium? Mg’s atomic number is 12, so there must be 12 protons and it is an atom, so there must be 12 electrons 37)How many protons, neutrons and electrons are there in an atom of barium-136? Barium has an atomic number of 56, so there are 56 protons and 56 electrons. Its mass is 136 so 56 + n = 136 therefore # no is 80 38) – if you have questions on this one make sure you understand number 37 first… Isotope Symbol # p+ #e - #no Atomic Mass Charge Name Number Number 118 tin - 118 68 0 50 50 50 118 Sn 40 K +1 19 50 Potassium-40 19 18 21 19 40 +1 9 10 10 9 19 -1 7 10 7 7 14 -3 52 52 76 52 128 0 Fluorine -19 19 F -1 9 Nitrogen -14 14 7 N -3 128 tellurium - 128 52 Te 46)Complete this chart on the three types of radioactive decay Type Alpha Beta Gamma Symbol Mass (amu) 4 amu 0 amu 0 amu Charge +2 -1 No charge 238 47) If the radioactive atom 92U emits an alpha particle, the atom remaining is represented by (A) 238 92U (B) 236 92Th (C) 234 92U (D) 234 90Th 234 (E) 91Pa The alpha particle is two protons and two neutrons, so the mass will decrease by 4 and the atomic number by 2… 238-4 = 234 92-2 = 90 30 14Si 48) What term completes this equation? 4 2 (A)2He 1 (B)1H 32 0 + ? 16S + –1e 0 (C)1H (D) –1e The mass must be equal on both sides of the equation 30 + x = 32 + 0 x = 2 The atomic numbers must be equal on both sides 14 + x = 16-1 x =1 214 49) What particle is emitted when lead–214, 82Pb, undergoes natural radioactive 214 decay to bismuth–214, 83Bi? 4 (A) an alpha particle, 2He (C) 1 a proton, 1H 0 1 (B) a beta particle, –1e (D) a neutron, 0n The atomic number increases while the mass remains constant. The beta particle 0-1e is the only way to show this – remember that this decay is when a neutron turns into a proton and an electron and the electron is shot out of the nucleus. 53) Which type of radiation has a +2 charge? a. Alpha (2 p+ and 2 no) b. beta c. gamma d. neutron 54) Which type of radiation generates the highest energy – is the “hardest” to block? a. Alpha b. beta c. gamma d. neutron 55) make sure to add the values correctly 234 4 a. 238 92 U 19 0 90 Th + 2He c. 222 218 86 84 Rn alpha b. 9 19 F -1 + 10Ne Beta 4 Po + 2 He alpha d. 210 85 210 0 At 86 Rn +- 1 beta 56) What element was the first synthesized by scientists (namely) Ernest Rutherford? Oxygen-17 – read your book 57) How many grams of sample are left after 20 minutes if 100 grams start decaying with a half life of 5 minutes? 100g 50g in 5 min 25g in 10 min 12.5g in 15 min 6.25 g in 20 min 58) How long will it take 100 grams of radioactive sample to decay so that only 6.25 grams remain and the samples half life is 3 days? 100g in 3 days 50g 25g in 6 days 12.5g in 9 days 6.25 g in 12 days 59) How long is the half life of an isotope if 2.0 grams of sample remain from a 64 gram sample after 30 years? 64g 32g 16 g 8 g 4 g 2 g there are 5 half lives in 30 years, each half life must be 6 years long.