Atomic Structure: 1. The smallest particle of an element that retains the properties of that element is a(n) ____. 2. The chemical symbol for the element iron is ____. 3. In which of the following is the number of neutrons correctly represented? 4. Which of the following sets of symbols represents isotopes of the same element? 5. How do the isotopes hydrogen-1 and hydrogen-2 differ? 6. Which of the following is true about subatomic particles? 7. Ernest Rutherford's "gold foil" experiment helped explain that an atom _____. 8. The nucleus of an atom _____. 9. What particle is needed to complete this nuclear reaction? 10. What is the change in atomic mass when an atom emits gamma radiation? 11. Which of the following materials is most effective for stopping gamma radiation? 12. Protons exhibit an electrostatic force that repels other protons. Despite this force, neutrons and protons are held together by a(n) _____. 13. The element chromium has four naturally occurring isotopes. Use the relative abundance of each to calculate the average atomic mass of chromium. Cr = 4.34%, Cr = 83.79%, Cr = 9.50%, Cr = 2.37% 14. Cobalt–60 has a half–life of 5.25 years. How much of the substance would remain after two half–lives? 15. Radiometric dating is possible because the rates of decay of radioactive isotopes ____. 16. What types of atomic orbitals are in the third period on the Periodic Table? 17. What is the maximum number of electrons in the second principal energy level? 18. What is the number of electrons in the outermost energy level of an oxygen atom? 19. The Periodic Table can be divided into sections, or blocks, which correspond to the sublevels that are being filled with valence electrons. In the Periodic Table shown below, which sequence lists these blocks in s, p, d, f order? Rn Po + _____ 20. What is the electron configuration of the calcium? 21. Energy released by an electron moving to a lower energy level can be observed as _____. 22. Based on the observed red shifts in the spectral lines of distant galaxies, astronomers conclude that ____. 23. All stars, regardless of size, eventually ____. 24. In the Milky Way, the most abundant gas in emission nebulae is ____. 25. In the cores of extremely hot red giants, nuclear fusion convert helium to ____. 26. The elements of the Periodic Table are arranged _____. 27. Elements in the same group tend to have similar reactivities because they have the same number of _____. 28. Which of the following elements are characterized by having full outermost s and p orbitals? 29. Of the elements Fe, Hg, U, and Te, which is a representative element? 30. Group 1A elements on the Periodic Table are _____.