Unit 1 Atomic Structure Study Guide Key

ANSWER KEY Unit 1 Outline –Atomic Structure and Nuclear Chemistry Essential Skills & Concepts 1. 2. 3. 4. 5. Describe the basic structure of an atom by: a) Knowing the part that contains most of the mass & the part that contains most of the volume in an atom. B) Understanding how “electrostatic forces” and “nuclear forces” hold an atom together. Using the periodic table, determine the number of protons, neutrons, electrons and the atomic mass of any element. For alpha, beta, and gamma radiation: a) Describe how the nucleus changes b) describe the different types of damage they can do in matter c) the different types of penetration Describe how energy released during nuclear reaction (fusion/ fission) is much greater than chemical reactions (as calculated by E = mc2)- mass defect. Explain how some isotopes of elements are radioactive, as are the ones formed in nuclear reactions. Vocabulary Terms Atom Element Electron cloud Nucleus Electron Neutron Proton Atomic number Atomic mass unit (amu) Average atomic mass Mass number Mass volume Isotopes Electromagnetic/ electrostatic Force Nuclear Forces Radioactive decay Band of Stability Gamma ray Beta particle Alpha particle Nuclear reaction Nuclear Fusion Nuclear Fission Chemical reaction Half-life Mass Defect Rutherford Study Guide- (this is only a partial review- use your worksheets, notes, & labs too) 1. Subatomic particle Proton Neutron Electron Location in atom Nucleus Nucleus Electron Cloud Charge + 0 - 2. a. Which subatomic particles account for most of an atom’s mass? 1 amu 1 amu 1/2000th b. Volume? a. Protons + Neutrons (or nucleus) 3. a. What is the charge of the nucleus? Size (mass) b. Electrons / electron cloud b. Show how this is determined? a. Positive b. There are only protons (+) and neutrons (no charge) in the nucleus 4. a. What is the overall charge of an oxygen atom? b. Show how this is determined? a. neutral b. There are equal numbers of protons (+) and electrons (-) in the atom. 5. a. Name and describe the force that keeps the electrons confined in the space surrounding the nucleus. . Electrostatic/ Electromagnetic Forces - the negatively charged electrons are attracted to the positively charged protons in the nucleus b. Name and describe the force that keeps the nucleus from breaking apart. Nuclear Force/ Strong Force - The protons in the nucleus should try to repel each other based on the electrostatic forces, however, this does not happen because the nuclear force overpowers the repulsion and keeps the nucleus together. Hyphen notation Atomic number Avg. atomic mass Mass number P+ e- N0 S-32 16 32.07 32 16 16 16 32 16 Ca-44 20 40.08 44 20 20 24 44 20 Zn- 64 30 65.39 64 30 30 34 64 30 F-19 9 19.00 19 9 9 10 19 9 Nuclear notation S Ca Zn F 7. Given: Carbon- 12 and Carbon- 14 a) What are the 2 versions called? isotopes b) What’s the same between C-12 & C-14? The number of protons and electrons c) What’s different? The mass (because of the different number of neutrons) 8. a. What did Ernest Rutherford discover about atoms? b. How did he perform his experiment? a. He discovered that atoms are mostly empty space and that there was a tiny, positive mass called a nucleus b. He shot alpha particles at gold foil and observed how the particles were deflected. 9. Compare an atom, an element, a molecule by drawing them. atom= the smallest unit of an element that still retains the properties element= a bunch of atoms of the same type (can be bonded or not) molecule= Atoms bonded together (can be the same or different atoms) 10 a. What determines whether an atom will be radioactive? b. Explain how unstable atoms gain stability. a. The ratio of neutrons to protons (small atoms are stable with 1 neutron : 1 proton, large atoms are stable with 1.5 neutrons : 1 proton). b. Atoms gain stability by undergoing radioactive decay- they lose particles from their nucleus and energy. This makes them more stable. 11. Write the symbol used to denote alpha, beta, and gamma radiation and give their mass and charge. Greek Symbol Name of symbol Particle released in Nuclear Rxn α Alpha Helium nucleus β beta Electron γ gamma Photon (electromagnetic energy) Nuclear Notation 4 2 0 1 0 0Y Charge Penetration He + Low e - med 0 high 12. Fill in the missing part and name the type of decay: 226 88 a 4 2 Ra He 0 1 _____ e ______ 237 93 Np 0 0 B c) Si-35 undergoes beta decay. Write the reaction. 35 14 0 1 Si e 35 15 Answers: 222 86 Rn 237 92 U Type: Alpha Gamma & Beta P 13. a. What does the term “½ life” mean when referring to a radioactive isotope? Time it takes for ½ of a radioactive substance to break down into a stable isotope. b. The half-life of K-42 is 12.4 hours. How much of a 750 g sample is left after 62.0 hours? (show work) 62 hours/ 12.4 hours= 5 half lives 750  375 187.5 93.75  46.875  23.44 g Or using math… (62.0hours) x 1 750 g x 2 1half life 12.4hours 5half lives 5 23 gram of K-42 left. 14. Explain 2 ways in which nuclear reactions differ from chemical reactions? Nuclear- changes the identity of the nucleus (protons/ neutrons) and the atom is changed & has the potential to release large amounts of energy. Chemical- involves the re-arranging of atoms & releases less energy than a nuclear reaction. 15. Explain how the mass defect and E = mc2 account for the large amounts of energy released during nuclear reactions. Anytime a nucleus is altered (ex: fission/ fusion) mass appears to go missing (aka the mass defect). However, Einstein’s equation E= mc2 describes what happens to the mass that is “lost” during a nuclear reaction it is turned into energy. This helps account for the tremendous amount of energy released during nuclear reactions. 16 a. Differentiate between 2 types of nuclear reactions: nuclear fission and nuclear fusion In a fission reaction a single nucleus is split into two nuclei. In a fusion reaction, two small nuclei are combine to make a single, larger nucleus. b. Which is most commonly used on our planet? Fission is most commonly used on our planet (nuclear reactors, nuclear bombs).