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. Given the electron dot diagram: The valence electrons represented by the electron dot diagram could be those of atoms in Group 1. 13 2. 15 3. 3 4. 16 -------------- 2. Which statement best describes the nucleus of an aluminum atom? 1. 2. 3. 4. It has a charge of +13 and is surrounded by a total of 10 electrons. It has a charge of +13 and is surrounded by a total of 13 electrons. It has a charge of −13 and is surrounded by a total of 10 electrons. It has a charge of −13 and is surrounded by a total of 13 electrons. -------------- 3. Base your answer to the question on the information below. An atom has an atomic number of 9, a mass number of 19, and an electron configuration of 2-6-1. Figure 1 Explain why the number of electrons in the second and third shells shows that this atom is in an excited state. Answer: -------------- 4. Which of these phrases best describes an atom? 1. 2. 3. 4. a positive nucleus surrounded by a hard negative shell a positive nucleus surrounded by a cloud of negative charges a hard sphere with positive particles uniformly embedded a hard sphere with negative particles uniformly embedded -------------- 5. Which atoms represent different isotopes of the same element? 1. and 2. and 3. and 4. and -------------- 6. Which of the following atoms has the greatest nuclear charge? 1. Al 2. Ar 3. Si 4. Na -------------- 7. What is a possible mass number of a sodium atom? 1. 1 2. 11 3. 12 4. 23 -------------- 8. Write an electron configuration for a silicon atom in an excited state. Answer: -------------9. The atomic mass of an element is defined as the weighted average mass of that element’s 1. 2. 3. 4. most abundant isotope least abundant isotope naturally occuring isotopes radioactive isotopes -------------- 10. What is the total number of electrons present in an atom of 1. 27 2. 32 ? 3. 39 4. 86 -------------- 11. What is the total number of electrons in a Cu+ ion? 1. 28 2. 29 3. 30 4. 36 -------------- 12. What are the nucleons in an atom? 1. protons and electrons 2. protons and neutrons 3. neutrons and electrons 4. neutrons and positrons -------------- 13. Which particle contains the greatest number of electrons? 1. Na 2. Na+ 3. F 4. F− -------------- 14. What is the total number of neutrons in an atom of 1. 82 2. 125 ? 3. 207 4. 289 -------------- 15. Which atoms contain the same number of neutrons? 1. and 2. and 3. and 4. and -------------- 16. An atom in the ground state contains 8 valence electrons. This atom is classified as a 1. metal 2. semimetal 3. noble gas 4. halogen -------------- 17. Which diagram represents the nucleus of an atom of ? 1. 3. 2. 4. -------------- 18. If 75.0% of the isotopes of an element have a mass of 35.0 amu and 25.0% of the isotopes have a mass of 37.0 amu, what is the atomic mass of the element? 1. 35.0 amu 2. 35.5 amu 3. 36.0 amu 4. 37.0 amu -------------- 19. Which ion has the same electron configuration as an H− ion? 1. Cl− 2. F− 3. K+ 4. Li+ -------------- 20. Base your answer on the data table, which shows three isotopes of neon. In terms of atomic particles, state one difference between these three isotopes of neon. Answer: -------------- Answer Key for atomic structure 1. 1 8. 15. 4 Acceptable responses include, but are not limited to: 2. 2 3. Examples: 4. 2 5. 3 6. 2 2-7-5 1-8-5 2-8-3-1 9. 3 10. 1 16. 3 17. 2 11. 1 12. 2 13. 1 18. 2 19. 4 20. The third shell has one electron before the second shell is completely filled. The electron configuration is not 2-7, which is the ground state for an atom with atomic number 9. Acceptable responses include, but are not limited to, these examples: 7. 4 14. 2 Each isotope has a different number of neutrons. different number of neutrons Ne-22 has two more neutrons than Ne-20 and one more neutron than Ne-21.