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Reading Science Atoms Matter and Energy Name: Date: READING SCIENCE The History of Atomic Theory (Lexile 820L) 1 Since the ancient Greek civilization, people have wondered about the nature of the atom. The atom is the basic building block of matter. The word “atom” comes from the Greek language. “A…” is a prefi x meaning “not.” The word “tomos” means “cut.” Therefore, “atomos” or “atoms” means “cannot be cut or divided.” 2 Many people helped develop the theory of atoms. The fi rst was a Greek named Democritus in the 4th century BC. He proposed that all matter was made Plum Pudding Model of tiny particles. Democritus thought that empty space fi lled the area between the solid atoms. That concept of the atom was unchanged for centuries. Then an English scientist, John Dalton, proposed an “atomic theory” in 1803. Atomic theory says that atoms are solid with an atomic mass. They can react because of the forces of attraction and repulsion. In 1873, James Clerk Maxwell proposed that electric and magnetic fi elds fi lled the empty space in atoms. 3 In 1897, J. J. Thomson discovered the fi rst subatomic particles which he called electrons. His experiments found that these electrons have a negative electric charge. He then calculated that they had a much smaller mass than even the smallest atom. Thomas proposed the plum pudding model of the atom. This model says that negatively-charged electrons are mixed inside a cloud of positive charge. He thought they were like chunks of plum inside pudding. 4 Ernest Rutherford did an experiment in 1909 to test Thomson’s model. His results did not agree with the plum pudding model. Instead, Rutherford was the fi rst to show the nuclear model of the atom. This model shows that the center of an atom contains positively- charged protons (p+) surrounded by the negatively-charged electrons (e-). In 1932, Sir James Chadwick found the neutrally charged neutron (n0). The atomic model now seemed complete after all these discoveries. 5 Many people had a hand in developing atomic theory as we know it today. However, scientists continue to study the atom. They have found many more details about atoms. As we learn aboutSample this building block of matter, the nuclear model of the atom will continue to change. © 2013-2014 Accelerate Learning - 1 All Rights Reserved 8.5A_2.0_ELABORATE_ReadingScience_820L_BE.indd 1 12/6/13 11:31 AM Atoms READING SCIENCE Matter and Energy 1 The root word “di” means “two,” so the word “diatomic” refers to _____. A forces within the atom B a molecule with two atoms C negatively-charged electrons D positively-charged protons 2 In paragraph 2, attraction and repulsion refer to _____. A electric and magnetic fi elds B atomic theories C tiny particles D solid atoms 3 How did Ernest Rutherford’s experiment relate to J.J. Thomson’’s work? A Rutherford looked for magnetic fi elds while Thomson looked for electric fi elds. B Rutherford repeated Thomson’s experiment and confi rmed the results. C Rutherford tested a conclusion based on Thomson’s results. D RutherfordSample had not known about Thomson’s experiment. © 2013-2014 Accelerate Learning - 2 All Rights Reserved 8.5A_2.0_ELABORATE_ReadingScience_820L_BE.indd 2 12/6/13 11:31 AM Atoms READING SCIENCE Matter and Energy 4 Which scientist discovered the neutron and gave us the current basic model of the atom? A James Maxwell B John Dalton C James Chadwick D Sir Isaac Newton 5 What contribution did J.J. Thomson make to the development of atomic theory? A Said that atoms are solid masses B Showed that electrons surround a dense nucleus C Found that atoms are made of smaller particles D Proposed that atoms contain electric fi elds Sample © 2013-2014 Accelerate Learning - 3 All Rights Reserved 8.5A_2.0_ELABORATE_ReadingScience_820L_BE.indd 3 12/6/13 11:31 AM Atoms Matter and Energy Name: Date: WRITING SCIENCE LOOK THINK Think about the definition of an atom. WRITE Describe the structure of an atom. Be sure to – • Address the prompt, provide support, and conclude your thoughts. • Write legibly and concisely. Notes Sample © 2013-2014 Accelerate Learning - 4 All Rights Reserved 8.5A_2.0_EVALUATE_WritingScience_K2.indd 4 12/6/13 11:31 AM Atoms WRITING SCIENCE Matter and Energy Topic: Sample © 2013-2014 Accelerate Learning - 5 All Rights Reserved 8.5A_2.0_EVALUATE_WritingScience_K2.indd 5 12/6/13 11:31 AM Sample STEM_K.6CD_2.0_Explain_STEMscopedia_ENG.indd 30 11/18/13 8:31 AM Protons and Electrons Matter and Energy Name: Date: READING SCIENCE Protons and Electrons (Lexile 810L) 1 Our current model of how the atom is made has protons in a nucleus and orbiting electrons. This idea developed over many years. It is the result of the work of many scientists. A major step was made in 1911 by Ernest Rutherford. Building on the work of Eugen Goldstein, Wilhelm Wein, and J. J. Thomson, he discovered the nucleus. Rutherford is often called the Father of Nuclear Science. 2 Rutherford studied Thomson’s model of the atom. He wanted to prove that it was right. Thomson’s model said that electrons were mixed in the sphere of the atom, like raisins in a plum pudding. Rutherford did the “gold foil” experiment to test this theory. 3 In the “gold foil” experiment, Rutherford discovered that the mass of the atom is not spread as evenly as Thomson thought. Rutherford shot radiation particles at a thin sheet of gold. He expected them to go straight through. Instead, a few particles bounced off the foil instead of passing through it. He fi gured out that the center of an atom is made of a dense, positively-charged middle. This nucleus is surrounded by negatively-charged electrons. 4 Rutherford’s nuclear model of the atom triggered other advances. One was that scientists learned how important the proton is. The proton also got its name which comes from Greek meaning “fi rst.” Goldstein and Wein had discovered the proton years before. However, no one realized what it was until Rutherford’s work on the nucleus. Antonius van den Broek soon proposed that protons determined an element’s identity. He also said that elements should be arranged in the Periodic Table based on the number of protons. 5 Physicist Neils Bohr improved Rutherford’s nuclear model of the atom. He said that electrons move around the nucleus in different energy levels. Part of his theory says that only valence electrons occupy the outermost shell of the electron cloud of an atom. Scientists realized that the chemical properties of elements are related to their electron confi gurations. Chemical properties describe an element’s reactivity. Bohr and G. N. Lewis found that valence electrons control the way the atom will react with other atoms. In other words, valence electrons give an atom its chemical properties. 6 The atomic model is the work of many scientists over many years. This is true of most scientifi c theory. They have come up with theories, done experiments, and shared fi ndings. The result isSample that we now understand how atoms are put together. © 2013-2014 Accelerate Learning - 7 All Rights Reserved 8.5B_2.0_ELABORATE_ReadingScience_810L_BE.indd 7 12/6/13 11:31 AM Protons and Electrons READING SCIENCE Matter and Energy 1 Which of the following choices places the scientists in order from earliest to latest based on their contribution to our understanding of atomic structure described in this passage? A Lewis, Wein, Goldstein B Rutherford, Goldstein, Bohr C Bohr, Rutherford, Thomson D Thomson, van den Broek, Lewis 2 Thomson’s model suggested that electrons were mixed into the sphere of an atom much like raisins in ____. A muffi ns B plum pudding C a box D toast 3 What did Rutherford’s experiment prove about the atomic nucleus? A It is like a raisin muffi n, with a positively-charged core. B It is densely clustered in the middle of the atom. C It was unknown by the means that Rutherford had access to at the time of the experiment. D It is madeSample of electrons and neutrons. © 2013-2014 Accelerate Learning - 8 All Rights Reserved 8.5B_2.0_ELABORATE_ReadingScience_810L_BE.indd 8 12/6/13 11:31 AM Protons and Electrons READING SCIENCE Matter and Energy 4 Based on the descriptions in the passage, which scientist proposed a model of the atom that matches the above diagram? A Ernest Rutherford B Neils Bohr C J.J Thomson D Antonius van den Broek 5 What is the main point of the passage? A Scientifi c theories often come about as a result of many people. B Atoms have only been identifi ed in the past 100 years. C Gold foil is the only type of material that can be used to fi nd the mass of atoms. D ScientistsSample do not use others’ work in forming their theories. © 2013-2014 Accelerate Learning - 9 All Rights Reserved 8.5B_2.0_ELABORATE_ReadingScience_810L_BE.indd 9 12/6/13 11:31 AM Protons and Electrons Matter and Energy Name: Date: WRITING SCIENCE LOOK THINK Think about how valence electrons participate in the formation of chemical bonds with other atoms. WRITE Explain how protons determine an element’s identity and valence electrons determine its chemical properties. Be sure to – • Address the prompt, provide support, and conclude your thoughts. • Write legibly and concisely. Notes Sample © 2013-2014 Accelerate Learning - 10 All Rights Reserved 8.5B_2.0_EVALUATE_WritingScience_K2.indd 10 12/6/13 11:31 AM Protons and Electrons WRITING SCIENCE Matter and Energy Topic: Sample © 2013-2014 Accelerate Learning - 11 All Rights Reserved 8.5B_2.0_EVALUATE_WritingScience_K2.indd 11 12/6/13 11:31 AM Sample STEM_K.6CD_2.0_Explain_STEMscopedia_ENG.indd 30 11/18/13 8:31 AM Periodic Table Matter and Energy Name: Date: READING SCIENCE Mendeleev and His Periodic Table (Lexile 740L) 1 Russian chemist, Dmitri Mendeleev, knew scientists needed to be able to identify an element easily.
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