Understanding the Atom

Transcription

1 Name Date Period 3.1 Discovering Parts of an Atom Directions: On the line before each statement, write correct if the statement is correct or not correct if the statement is not correct. If the statement is not correct, change the underlined word(s) to make it correct. (30 points this side) 1. Early Greek philosophers, such as Democritus, thought that all matter was made of fire, water, air, and earth. 2. John Dalton s atomic theory supported some of the ideas of Aristotle. 3. An atom is the smallest piece of an element that still represents the element. 4. Atoms are so small that about 7.5 million carbon atoms could fit into the period at the end of this sentence. 5. An electron is a particle with one negative charge. 6. Rutherford s atomic theory stated that most of an atom s mass is concentrated in the nucleus. 7. Niels Bohr discovered the existence of neutrons, or neutral particles, in the nucleus of an atom. 8. According to the modern atomic model, electrons form an electron cloud around the nucleus. 9. Modern scientists believe that protons and neutrons are not made of smaller particles. Directions: Answer each question. 10. Is it possible to see atoms with your eyes? Explain. 11. What is an STM? 12. How have STMs helped scientists study atoms? Understanding the Atom Matching Directions: On the line before each definition, write the letter of the term that matches it correctly. Not all terms are used. Write the terms NOT USED and a definition. 1. particle with one negative charge 2. smallest particle of an element that still represents that element 3. particle with one positive charge 4. neutral particle found in the nucleus A. nucleus B. electron C. neutron D. proton E. quark F. atom Directions: Label this diagram by writing the correct term from the word bank on each line. electron cloud neutron nucleus proton 1 Utah Core Curriculum Standard I Davis School District Buffalo Book Chapter 3 Online Physical Science Bubble Book Chapter 9

2 Name Date Period A. Early Ideas About Matter (40 points this side) 2. The results showed that most of the particles traveled through the 1. Many ancient Greek philosophers thought that all matter was made of only four elements fire, water, air, and. 2. These early scientists were not able to their theories. 3. Democritus proposed that matter is made of small, indivisible objects called. 4. He proposed that different types of are made from different types of atoms. B. Dalton s Atomic Model 1. John Dalton proposed the theory, which was based on careful observations and of chemical reactions. 2. Dalton s theory states that atoms cannot be divided,, or destroyed. 3. It also stated that atoms of one are different from atoms of other. C. The Atom 1. A(n) is the smallest piece of an element that still represents that element. 2. Atoms were first seen by using a(n) microscope. D. Thomson Discovering Electrons 1. Thomson discovered that the rays in a(n) were attracted to a(n) charged plate, which means that the rays have a(n) charge. 2. Thomson s atomic model stated that an atom is a positively charged with throughout it. E. Rutherford Discovering the Nucleus 1. Rutherford s student performed an experiment during which they shot particles into a piece of foil. foil, but some bounced to the, and a few bounced straight back. 3. Rutherford s resulting atomic model proposed that most of an atom s and charge is concentrated in the center of the atom. a. The is the small, positively charged area in the center of the atom. b. In the nucleus is the, which is an atomic particle with one positive charge. F. Discovering Neutrons 1. was one of Rutherford s colleagues. 2. Chadwick discovered the, a neutral particle that exists in the of an atom. G. Bohr s Atomic Model 1. The atomic model of proposed that move in circular orbits, or, around the nucleus. 2. When energy is added to an atom, electrons move to higher ; when energy is released by the electron, it moves back to a lower level. 3. The limitation of Bohr s model is that electrons do not actually move in orbits. H. The Modern Atomic Model 1. In modern atomic theory, electrons form a(n), which is an area around the in which an electron is likely to be located. 2. An electron cloud is mostly space. I. Quarks 1. Protons and are made of smaller parts called. 2. There are types of quarks. 2 Utah Core Curriculum Standard I Davis School District Buffalo Book Chapter 3 Online Physical Science Bubble Book Chapter 9

3 (30 points this side) Name Date Period Directions: Complete the crossword puzzle with the correct terms from the word bank. Atomic Theory Magic Square Put the number of the definition from the list below on the line in the square with the appropriate term. Check your answers by adding the numbers in each row and column. They should add up to the same number. Democritus Dalton Thomson element atoms electron electron cloud neutron nucleus proton Rutherford proton atom Bohr quark neutron nucleus alpha particle electron Chadwick energy levels electron cloud 1. current explanation of where electrons might be found in the atom 2. English schoolteacher who proposed the atomic theory model of matter 3. proposed the plum-pudding model of the atom; discovered the electron 4. the negative particle that circles the nucleus 5. developed the model of the atom in which electrons orbit the nucleus in energy levels 6. the neutral particle in the nucleus of an atom 7. the tiny positive core of an atom; contains protons and neutrons 8. discovered the nucleus using his gold foil experiment 9. small particles that make up protons and neutrons 10. the smallest particle of an element that has the properties of that element 11. the positive particle in the nucleus of an atom 12. used by Rutherford in his experiment; made of two protons and two neutrons 13. Greek philosopher who made a mental model of the atom 14. the paths in which electrons circle the nucleus according to the Bohr model 15. discovered the neutron 16. building blocks of matter represented by a symbol Across Down 1. particle with one negative charge (1 ) 3. small area in the center of an atom that contains most of the atom s mass 5. particle with one positive charge (1+) 2. area around the nucleus where an electron is most likely to be 4. neutral particle that exists in the nucleus of an atom 6. smallest pieces of elements that still represent those elements 3 Utah Core Curriculum Standard I Davis School District Buffalo Book Chapter 3 Online Physical Science Bubble Book Chapter 9

4 (45 points this side) Name Date Period 3.2 Protons, Neutrons, and Electrons How Atoms Differ A. The Parts of the Atom 1. and have about the same mass 2. have much less mass than the other two particles in an atom. 3. Most of the mass of an atom is in the. B. Different Elements Different s of Protons 1. The number of protons in an atom of an element is the element s. 2. Different elements contain different numbers of. 3. In a neutral atom, the number of equals the number of protons because the number of charges must equal the number of positive charges. C. Neutrons and Isotopes 1. are atoms of the same element that have different numbers of. 2. The total number of and neutrons in an atom is the of the atom. 3. The of an element is the average mass of the element s. a. The average atomic mass is according to the abundance of each isotope. b. Weighted means that the average atomic mass is based on the of each atom in a sample and the number of atoms of that that are present. D. Radioactivity 1. first noticed that some elements spontaneously give off energy. 2. _ called elements that spontaneously emit radiation radioactive. 3. Radiation is made of energy and that come from the of radioactive atoms. 4. When atoms release particles of radiation, they change to different. 5. is a process that occurs when an unstable changes into another, more stable nucleus by emitting radiation. a. Nuclear decay can produce three different types of. b. A(n) particle consists of protons and two. c. When alpha decay occurs, the atomic number of each atom that decays by. d. decay occurs when a neutron in an atom changes into a(n) and a high-energy electron called a(n) particle. e. When beta decay occurs, the atomic number of an atom by. f. Gamma rays contain a lot of but no particles.. g. rays are sometimes emitted during nuclear decay, but this decay does not change one element into another element. 6. Energy released during radioactive decay can be either or harmful. E. Ions Gaining or Losing Electrons 1. A(n) is an atom that is no longer neutral because it has gained or lost. 2. A positive ion is an atom that has electrons. 3. A negative ion is an atom that has electrons. 4 Utah Core Curriculum Standard I Davis School District Buffalo Book Chapter 3 Online Physical Science Bubble Book Chapter 9

5 Name Date Period 50 points this page Atomic Structure (42 points this column) 1. The atomic number represents the number of _. 2. In a neutral atom the number of protons is always equal to the number of _. 3. The mass number of an atom is the sum of the number of and the number of. Use a copy of the periodic table in your planner and the information given in the data table to fill in the blanks. (1 point each blank square) Extra credit: draw and label any of the atoms. Substance Symbol Atomic Mass of Protons of Neutrons of Electrons Helium 2 4 Mg Zinc Bromine Al Uranium Sodium Kr Calcium Ag Gold Copper Use Percentages Percentages compare a partial amount to a whole amount, much like a fraction. The whole amount is equal to 100%. To change a percentage into a decimal, first write the percentage as a fraction with a denominator of and then divide. For example, 25% equals, which is equal to A weighted average is a calculation based on the abundance, in percentages, of the items being averaged. Follow the steps below to calculate the weighted average atomic mass of an element. Copper (Cu) exists naturally in two isotopes. If copper is made up of 69.17% Cu-63 and 30.83% Cu-65, what is the average atomic mass of Cu? Step 1 Change each percentage to a decimal % = % = Step 2 Multiply the mass of each isotope by its decimal percentage = = Step 3 Add the values together to get the average atomic mass = Practice (8 points this column) 1. Boron (B) contains 19.9% B-10 and 80.1% B-11. What is the average atomic mass of boron? 2. If 50.69% of bromine (Br) is Br-79 and 49.31% is Br-81, what is the average atomic mass of bromine? 3. Silicon (Si) contains 92.23% Si-28, 4.67% Si-29, and 3.10% Si-30. What is the average atomic mass of Si? 4. If selenium (Se) is 0.89% Se-74, 9.36% Se-76, 7.63% Se-77, 23.78% Se- 78, 49.61% Se-80, and 8.73% is Se-82, what is the average atomic mass of Se? 5 Utah Core Curriculum Standard I Davis School District Buffalo Book Chapter 3 Online Physical Science Bubble Book Chapter 9

6 55 points this page Name Date Period Protons, Neutrons, and Electrons How Atoms Differ Directions: Use your textbook to answer each question. (5 points each sentence) 1. Atoms are composed of particles called protons, neutrons, and electrons. Describe the relative mass, the charge, and the location within the atom of protons, neutrons, and electrons. Key Concept How does a neutral atom change when its number of protons, electrons, or neutrons changes? Directions: Label this diagram by writing the correct number of electrons and protons on each line. Then use the diagram to answer each question on the lines provided There are 115 different elements. Each has its own distinct properties. Describe the way atoms of elements differ Most elements have different isotopes. Identify how atoms of isotopes differ from one another Some elements have an unstable nucleus that changes into a more stable nucleus through nuclear decay. Identify and describe three types of nuclear decay What does the diagram show? Neutral atoms sometimes gain or lose electrons. Atoms that are no longer neutral because they have gained or lost electrons are called ions. Describe the charge on an atom that has lost electrons. Then describe the charge on an atom that has gained electrons. 10. What happened to the electrical charge of each atom in the diagram? 11. The top left diagram shows sodium (Na). The bottom left diagram shows fluorine (F). Which symbols would you use to represent the top right diagram and the bottom right diagram? 6 Utah Core Curriculum Standard I Davis School District Buffalo Book Chapter 3 Online Physical Science Bubble Book Chapter 9

7 Name Date Period 20 points this page Radioisotopes You have learned that some isotopes of elements are radioactive. These are called radioisotopes. Radioisotopes are unstable, so they undergo decay by giving off radiation as matter and/or energy until they reach a more stable state. Half-Lives The rate at which radioisotopes of various elements decay is described as the half-life of the isotope. One half-life is the time it takes for one-half the atoms in a sample to decay. Half-lives for various radioisotopes can range from less than a second to billions of years. The table shows the half-lives for a number of radioisotopes. The number after each name is the isotope s atomic mass. Radioisotope Polonium-215 Barium-139 Iodine-131 Cobalt-60 Carbon-14 Uranium-238 Half-life seconds 86 minutes 8.07 days 5.26 years 5,730 years 4.5 billion years Using Half-Lives Suppose you begin with 10 g of barium-139, which decays to become lanthanum-139. After one half-life (86 minutes), you would have 5 g of barium-139 and 5 g of lanthanum-139. After another 86 minutes, half of the remaining 5 g of barium-139 would decay into lanthanum-139. You would now have 2.5 g of barium-139 and 7.5 g of lanthanum-139. How can we use this idea? Carbon Dating The half-lives of radioisotopes can help scientists determine the age of very old artifacts. For example, scientists can use the half-life of carbon-14 (C-14) to determine the approximate age of organic objects that are less than 40,000 years old. All living organisms contain a fixed percentage of the radioisotope C-14. When an organism dies, the C-14 is not replaced, but it continues to decay. By determining how much of the carbon-14 remains, scientists can calculate the age of a sample. This is known as carbon dating. Isotopes with longer half-lives such as uranium-238 can be used to date older objects such as igneous rocks. Applying Critical-Thinking Skills 1. Solve You began with 100 g of cobalt-60. How much cobalt-60 remains after years? 2. Explain The uranium used in fuel rods in nuclear power plants eventually decays to the point where it doesn t give off enough energy to be practical. Why might disposing of these rods be a problem if they contain uranium-238? 3. Make a bar graph showing how much is left after six half-lives. 105% 90% 75% 60% 45% 30% 15% Begin Utah Core Curriculum Standard I Davis School District Buffalo Book Chapter 3 Online Physical Science Bubble Book Chapter 9

8 Name Date Period 25 points this page Understanding the Atom Directions: On the line before each statement, write correct if the statement is correct or not correct if the statement is not correct. If the statement is not correct, change the underlined word(s) to make it correct. 1. A proton has a charge of Neutrons and protons have the same relative mass. 3. The number of electrons in an atom of an element is the element s atomic number. 4. Neutral atoms have the same number of protons and electrons. 5. Carbon-12 and carbon-13 are isotopes, so they have different numbers of neutrons. 6. The mass number of an atom can be determined by adding the number of electrons and the number of neutrons. Key Concept How has the atomic model changed over time? Directions: Place the events in chronological order from earliest to most recent by writing a number 1 through 7 on the line before the statement that describes each event. J.J. Thomson investigates the electrical charges of atoms. Democritus challenges the popular idea that matter is made of fire, water, air, and earth. Niels Bohr investigates the energy level of electrons. Students of Ernest Rutherford conduct the gold foil experiment. John Dalton finds evidence to support the theory that all matter is made of atoms that cannot be divided, created, or destroyed. Scientists discover that protons and neutrons are made of quarks. James Chadwick discovers that in addition to protons, the nucleus also contains neutrons. Directions: On each line, write the term that correctly replaces the underlined words in each sentence. 1. Carbon-12, carbon-13, and carbon-14 are examples of atoms of the same element that have different numbers of neutrons. 2. Radioactive elements emit radiation without external force or cause. 3. Nitrogen s number of protons is seven. 4. A radioactive element goes through a process in which its unstable atomic nucleus changes into another more stable nucleus by emitting radiation. 5. Beneath each element s symbol on the periodic table, there is a number that provides the average mass of the element s isotopes, weighted according to the abundance of each isotope for the element. 6. Na + and F are examples of atoms that are no longer neutral because they have gained or lost electrons. 7. Uranium is an example of an element that is able to spontaneously emit radiation. 8. Carbon-12 is the most abundant isotope of the element; it has a sum of protons and neutrons equal to Utah Core Curriculum Standard I Davis School District Buffalo Book Chapter 3 Online Physical Science Bubble Book Chapter 9