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Back Print Name Class Date Skills Worksheet Directed Reading A Section: The Atom HOW SMALL IS AN ATOM? ______ 1. 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. WHAT IS AN ATOM MADE OF? Match the correct description with the correct term. Write the letter in the space provided. ______ 2. particle of the nucleus that has no electrical charge ______ 3. particle found in the nucleus that is positively charged a. electron b. atomic mass unit (amu) c. nucleus ______ 4. particle with an unequal number of protons and electrons d. proton e. ion f. neutron ______ 5. negatively charged particle found outside the nucleus ______ 6. contains most of the mass of an atom ______ 7. SI unit used to express the masses of atomic particles HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER? 8. The simplest atom is the atom. It has one and one . 9. Neutrons in the atom’s keep two or more protons from moving apart. 10. If you build an atom using two protons, two neutrons, and two electrons, you have built an atom of . 11. An atom does not have to have equal numbers of and . Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 3 Introduction to Atoms Back Print Name Class Date Directed Reading A continued 12. The number of protons in the nucleus of an atom is the of that atom. ISOTOPES ______13. Isotopes always have a. the same number of protons. b. the same number of neutrons. c. a different atomic number. d. the same mass. ______14. Which of the following is NOT true about unstable atoms? a. They are radioactive. b. They have a nucleus that always remains the same. c. They give off energy as they fall apart. d. They give off smaller particles as they fall apart. ______15. What is the mass number of an isotope that has 5 protons, 6 neutrons, and 5 electrons? a. 1 c. 10 b. 11 d. 16 ______16. If carbon has an atomic number of 6, how many neutrons does carbon-12 have? a. 12 c. 6 b. 8 d. 18 17. Most elements contain a mixture of two or more . 18. The weighted average of the masses of all the naturally occurring isotopes of an element is the . FORCES IN ATOMS Match the correct definition with the correct term. Write the letter in the space provided. ______19. helps protons stay together in the nucleus a. gravitational force ______20. pulls objects toward one another b. electromagnetic force ______21. an important force in radioactive atoms c. strong force ______22. holds the electrons around the nucleus d. weak force Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 4 Introduction to Atoms Back Print Name Class Date Skills Worksheet Section Review The Atom USING KEY TERMS 1. Use the following terms in the same sentence: proton, neutron, and isotope. Complete each of the following sentences by choosing the correct term from the word bank. atomic mass unit mass number atomic number atomic mass 2. An atom’s is equal to the number of protons in its nucleus. 3. An atom’s is equal to the weighted average of the masses of all the naturally occurring isotopes of that element. UNDERSTANDING KEY IDEAS ______ 4. Which of the following particles has no electric charge? a. proton c. electron b. neutron d. ion 5. Name and describe the four forces that are at work within the nucleus of an atom. MATH SKILLS 6. The metal thallium occurs naturally as 30% thallium-203 and 70% thallium-205. Calculate the atomic mass of thallium. Show your work below. Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 18 Introduction to Atoms Back Print Name Class Date Section Review continued CRITICAL THINKING 7. Analyzing Ideas Why is gravitational force in the nucleus so small? 8. Predicting Consequences Could a nucleus of more than one proton but no neutrons exist? Explain. INTERPRETING GRAPHICS 9. Look at the two atomic models below. Do the two atoms represent different elements or different isotopes? Explain. Proton Neutron Proton Neutron Electron Electron Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 19 Introduction to Atoms