Skills Worksheet Directed Reading A Section: Development of the Atomic Theory THE BEGINNING OF ATOMIC THEORY Write the letter of the correct answer in the space provided. 1. Around 440 BCE, who thought that matter is made of particles that cannot be cut? a. Bohr b. Dalton c. Aristotle d. Democritus 2. What does the word atom mean? a. dividable b. invisible c. hard particles d. not able to be divided (pp. 164 171) 3. What is the smallest particle into which an element can be divided? a. a nucleus b. a proton c. an atom d. a neutron DALTON S ATOMIC THEORY BASED ON EXPERIMENTS 4. Which of the following ideas was part of Dalton s atomic theory? a. All substances are made of atoms. b. Atoms can be divided. c. Atoms can be destroyed. d. Some substances are made of atoms. 5. What happened to Dalton s theory in the late 1800s? a. Dalton s theory was ignored. b. Dalton s theory was disproved. c. Dalton s theory was proved. d. Dalton s theory was changed. THOMSON S DISCOVERY OF ELECTRONS 6. What did Thomson discover about atoms? a. Atoms cannot be divided. b. There are small particles inside atoms. c. There are no small particles in atoms. d. All atoms have negative charges. Holt California Physical Science 66 Introduction to Atoms
Use the terms from the following list to complete the sentences below. electrons particles positively 7. Thomson discovered that a(n) charged plate in a cathode-ray tube attracted an invisible beam. 8. Thomson concluded that the beam was made of that have negative electric charges. 9. The negatively charged particles Thompson discovered are called. 10. Which of the following is true according to Thomson s plum-pudding model? a. Electrons are mixed throughout an atom. b. Electrons are in the center of an atom. c. Electrons are positively charged. d. Electrons are absent from an atom. RUTHERFORD S ATOMIC SHOOTING GALLERY 11. What did Rutherford expect all the charged particles to do? a. to pass right through the gold foil b. to deflect to the sides of the gold foil c. to bounce straight back d. to become blobs of matter 12. Which of the following statements is NOT true of Rutherford s results? a. Some of the particles turned to one side. b. Some of the particles did not move. c. Most of the particles passed through the gold foil. d. Some of the particles bounced straight back. THE NUCLEUS AND THE ELECTRONS 13. What did Rutherford revise in 1911? a. the atomic theory b. the particle theory c. the electron theory d. the scientific theory Holt California Physical Science 2 Introduction to Atoms
14. What positively charged area did Rutherford believe was in the center of an atom? a. an electron b. a nucleus c. a particle d. a proton 15. What important idea emerged from the results of Rutherford s experiment? a. Atoms are mostly empty space with no nucleus. b. Atoms are mostly electrons. c. Atoms are mostly empty space with a tiny, massive nucleus. d. Atoms have electrons in the nucleus. Bohr s Electron Levels 16. How did Bohr propose that electrons move around the nucleus? a. in a variety of ways b. haphazardly c. between the levels d. in definite paths The Modern Atomic Theory 17. What model represents current atomic theory? a. electron-cloud model b. plum-pudding model c. Rutherford s model d. Bohr s model 18. What is an atom s electron cloud? a. a region where electrons are never found b. a region where protons are likely to be found c. a region where neutrons are likely to be found d. a region where electrons are likely to be found Energy Levels 19. What is each electron s definite energy based on? a. its weight b. its size c. its location around the nucleus d. its location inside the nucleus Holt California Physical Science 3 Introduction to Atoms
THE SIZE OF AN ATOM 20. Which of the following statements is true? a. A penny has about 20,000 atoms. b. A penny has more atoms than Earth has people. c. Aluminum is made up of large-sized atoms. d. Aluminum atoms have a diameter of about 3 cm. Observing Atoms 21. Which of the following tools do scientists now use to observe atoms? a. light waves b. a scanning tunneling electron microscope c. a telescope d. a camera Holt California Physical Science 4 Introduction to Atoms
TEACHER RESOURCES Answer Key Directed Reading A SECTION: DEVELOPMENT OF THE ATOMIC THEORY 1. D 2. D 3. C 4. A 5. D 6. B 7. positively 8. particles 9. electrons 10. A 11. A 12. B 13. A 14. B 15. C 16. D 17. A 18. D 19. C 20. B 21. B SECTION: THE ATOM 1. A 2. C 3. E 4. D 5. C 6. A 7. B 8. C 9. electron 10. hydrogen 11. helium 12. neutrons 13. atomic number 14. element 15. periodic table 16. A 17. B 18. C 19. A 20. B 21. B 22. D 23. strong force 24. gravitational force 25. weak force 26. electromagnetic force Directed Reading B SECTION: DEVELOPMENT OF THE ATOMIC THEORY 1. D 2. atom 3. C 4. Dalton s results suggested that elements combine in specific proportions because they are made of atoms. 5. positively, negative 6. electrons 7. atom 8. A 9. Most of the particles passed right through the gold foil, some of the particles were deflected, and some of the particles bounced straight back. 10. D 11. Rutherford s model of the atom showed electrons surrounding the nucleus at a distance. 12. C 13. B 14. A 15. location around the nucleus 16. B 17. scanning tunneling electron microscope SECTION: THE ATOM 1. F 2. D 3. E 4. A 5. C 6. B 7. hydrogen, proton, electron (no particular order for proton and electron) 8. nucleus 9. helium 10. protons and neutrons (either order) 11. atomic number 12. A 13. B 14. B Holt California Physical Science 95 Introduction to Atoms