2. Main Ideas The ancient Greeks tried to explain matter, but the scientific study of the atom began with John Dalton in the early 1800's. An atom is made of a nucleus containing protons and neutrons; electrons move around the nucleus. The number of protons and the mass number define the type of atom. Unstable atoms emit radiation to gain stability.
10. Dalton’s Atomic Theory Even though some of the theory was incorrect, It provided the basis we have today for atomic theory. As is common with science, his theory has since been revised and additional information learned.
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12. Question ? Who was the first person to propose the idea that matter was not infinitely divisible? A. Aristotle B. Plato C. Dalton D. Democritus
13. Question? Dalton’s theory also conveniently explained what? A. the electron B. the nucleus C. law of conservation of mass D. law of Democritus
17. STM Scanning tunneling microscopy (STM) is the highest resolution imaging and nanofabrication technique available. It relies on quantum tunneling of electrons from a sharp metal tip to a conducting surface. The 71 Angstrom diameter "quantum corral" shown above was created and imaged with an ultra-high vacuum cryogenic STM. Each sharp peak in the circle is an iron atom resting on atomically flat copper
35. Question? Atoms are mostly ____. A. positive B. negative C. solid spheres D. empty space
36. Question? What are the two fundamental subatomic particles found in the nucleus? A. proton and electron B. proton and neutron C. neutron and electron D. neutron and positron
44. Question? An unknown element has 19 protons, 19 electrons, and 3 isotopes with 20, 21 and 22 neutrons. What is the element’s atomic number? A. 38 B. 40 C. 19 D. unable to determine
45. Question ? Elements with the same number of protons and differing numbers of neutrons are known as what? A. isotopes B. radioactive C. abundant D. ions
55. Question ? A reaction that changes one element into another is called what? A. chemical reaction B. beta radiation C. nuclear reaction D. physical reaction
56. Question ? Why are radioactive elements rare in nature? A. They do no occur on Earth. B. Most have already decayed to a stable form. C. They take a long time to form. D. They are too hard to detect.
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61. Question? Whose work led to the modern atomic theory? A. Dalton B. Rutherford C. Einstein D. Aristotle
62. Question? Which particle is not found in the nucleus of an atom? A. neutron B. proton C. dust D. electron
63. Question? Two isotopes of an unknown element have the same number of: A. protons B. neutrons C. electrons D. both A and C
64. Question? Lithium has an atomic mass of 6.941 and two isotopes, one with 6 neutrons and one with 7 neutrons. Which isotope is more abundant? A. 6 Li B. 7 Li C. Both isotopes occur equally. D. unable to determine
65. Question? What happens when an element emits radioactive particles? A. It gains energy. B. It gains neutrons. C. It loses stability. D. It loses energy.
66. Question? What is the smallest particle of an element that still retains the properties of that element? A. proton B. atom C. electron D. neutron
67. Question? How many neutrons, protons, and electrons does 124 54 Xe have? A. 124 neutrons, 54 protons, 54 electrons B. 70 neutrons, 54 protons, 54 electrons C. 124 neutrons, 70 protons, 54 electrons D. 70 neutrons, 70 protons, 54 electrons
68. Question? The primary factor in determining an atom's stability is its ratio of neutrons to ____. A. protons B. electrons C. alpha particles D. isotopes
69. Question? What is the densest region of an atom? A. electron cloud B. nucleus C. isotopes D. atomic mass
70. Question? Why are electrons attracted to the cathode in a cathode ray tube? A. The cathode is more stable. B. The cathode has a positive charge. C. The cathode has a negative charge. D. The cathode has no charge.
86. CIM Table 4.3 Properties of Subatomic Particles Figure 4.12 Rutherford's Experiment Figure 4.14 Features of an Atom Figure 4.21 Types of Radiation
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