CHM1 Exam 4 Review. Topics. 1. Structure of the atom a. Proton nucleus + 1 amu b. Neutron nucleus 0 1 amu c. Electron orbits - 0 amu 2.

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1 Topics 1. Structure of the atom a. Proton nucleus + 1 amu b. Neutron nucleus 0 1 amu c. Electron orbits - 0 amu 2. Atomic symbols Mass number (protons + neutrons) 4+ charge 126C atomic number (# protons) 3. Isotopes a. Average atomic mass = Sum of (isotope masses x percent abundances) 4. The major experiments a. Cathode Ray Tubes and the discovery of the electron J.J. Thompson i. Relative charge of the electron b. Oil drop experiment absolute charge of the electron Milikin c. Discovery of Neutrons Chadwick d. The Gold foil experiment Rutherford i. Most of the mass of the atom is in a small portion of the atom ii. The center of the atom must be positive 5. Atomic Models a. The Plum pudding model b. Bohr s model i. Similar to the solar system ii. Electrons jump from one orbit to another 1. Ground state 2. Excited states 3. Energy is absorbed when electrons jump out 4. Energy is emitted when electrons jump in. We observe light colors in some cases 5. Emission line spectra can be observed throughout the Electromagnetic spectrum a. IR low energy, long wavelength (>800 nm) b. Visible, colors, nm, ROYGBIV c. UV high energy, short wavelengths (<400 nm) 6. Electron Configurations shell number 1 (number of electrons in orbital) 1s letter designate subshell type Ground state carbon, 1s 2 2s 2 2p 6 Know the shapes of subshells s spherical p dumbbell d 4 leaf clover 1

2 Part A Multiple Choice. 1. The atomic mass of an element is calculated using the (1) atomic numbers and the ratios of its naturally occurring isotopes (2) atomic numbers and the half-lives of each of its isotopes (3) masses and the ratios of its naturally occurring isotopes (4) masses and the half-lives of each of its isotopes 2. Isotopes of an element must have different (1) atomic numbers (2) mass numbers (3) numbers of protons (4) numbers of electrons 6. A neutral atom contains 12 neutrons and 11 electrons. The number of protons in this atom is (1) 1 (3) 12 (2) 11 (4) Which electron configuration represents an atom of fluorine in the ground state? (1) 1s 2 2s 2 2p 6 (3) 1s 2 2s 2 2p 5 (2) 1s 2 2s 2 2p 5 5s 1 (4) 1s 2 2s 2 2p 4 5s 1 8. Which path represents a positively charged particle? 3. The nucleus of an atom contains (1) electrons, only. (2) neutrons, only. (3) protons and electrons. (4) protons and neutrons. 4. An electron has a charge of (1) 1 and the same mass as a proton (2) 1 and a smaller mass than a proton (3) +1 and the same mass as a proton (4) +1 and a smaller mass than a proton 5. What is the total number of neutrons in an atom of an element that has a mass number of 19 and an atomic number of 9? (1) 9 (3) 19 (2) 10 (4) 28 (1) A (2) B (3) C 9. How many electrons can occupy a p sublevel? (1) 2 (3) 6 (2) 4 (4) An atom of 17 O 2- has how many electrons? (1) 17 (3) 9 (2) 8 (4) The nucleus of an atom of K-42 contains (1) 19 protons and 23 neutrons (2) 19 protons and 42 neutrons (3) 20 protons and 19 neutrons (4) 23 protons and 19 neutrons 2

3 12. Which of the following was a conclusion of Rutherford s golf foil experiment? (1) The nucleus of an atom contains electrons. (2) The atom is mostly empty space. (3) The electron is negatively charged. (4) The nucleus contains neutrons. 13. Which atom or ion has the same electron configuration as a potassium ion, K +? (1) F - (3) Ne (2) Na + (4) Ar 14. Which of the following represents the shape of a p x orbital 15. The mass number of an isotope represents (1) the number of protons and electrons. (2) the number of electrons and neutrons. (3) the number of protons and neutrons. 16. Isotopes represent (1) different elements with different masses. (2) the same element with different masses. (3) different elements with the same mass. (4) the same element with the same mass. 17. How many neutrons are in an isotope of carbon- 13 (1) 6 (3) 8 (2) 7 (4) What is the maximum number of electrons that can occupy a d subshell? (1) (1) 2 (3) 10 (2) 6 (4) Which of the following is the symbol for a deuterium isotope of hydrogen? (1) 4 2H (3) 2 1H (2) 3 1H (4) 2 2H (2) 20. How many protons does a potassium atom contain? (1) 78 (3) 84 (2) 15 (4) Which of the following represents an isotope of oxygen? (1) 16 7X (3) 16 8X (2) 8 4X (4) 15 7X (3) 3

4 22. Which of the following is not a nucleon? (1) Proton (3) Electron (2) Neutron (4) Alpha particle 23. Which electron transition represents an absorption of energy? (1) from 2 nd to 3 rd shell (2) from 2 nd to 1 st shell (3) from 3 nd to 2 rd shell (4) from 3 nd to 1 st shell 24. How many protons does a sodium atom have? (1) 11 (3) 16 (2) 23 (4) What wavelength in the visible portion of the electromagnetic spectrum most likely corresponds to a red color? (1) 750 nm (2) 550 nm (3) 500 nm (4) 450 nm Free response. Provide written responses to the following questions, using complete sentences when appropriate and showing all work for calculations. 26. What were the major conclusions of Rutherford s gold foil experiment? 27. Complete the following table. Particle Mass (amu) Charge Location in the atom Proton Neutron Electron 28. (6 pts) Complete the following table. Atomic Symbol Number of Protons Number of Neutrons Number of Electrons 15 7N 5526Fe S 2-4

5 29. Explain the difference between the mass number of an isotope and the atomic mass of an element. 30. A new element has three isotopes with mass numbers of 288, 290 and 291. The atomic mass of this element is and the percent abundance of the heaviest isotope is 35%, what are the percent abundances of the other two isotopes? 31. Identify the two elements in the unknown atomic emission line spectrum nm 5

6 32. Explain how a bright-line spectrum is produced, in terms of electron jumping in the atom, excited states, quantized energy absorption or emission and the production of light energy. 33. Write the electron configuration for (a) O (b) H (c) P 3- (d) Li + 6

7 Answers (a) the atom is mostly empty space; (b) the nucleus is small and dense; (c) the nucleus is positively charged. 27. (a) 7, 8, 7; (b) 26, 29, 23; (c) 16, 17, The mass number is the sum of the protons and neutrons of an individual atom, whereas the atomic mass is the weighted average of all of the isotopes of an element %, and 7.5 % 30. Hydrogen and helium 31. Electrons must jump from a higher energy level to a lower energy level to emit light in descrete packets. 32. (a) [He]2s 2 2p 4 ; (b) 1s 1 ; (c) [Ne]3s 2 3p 6 ; (d) [He] 7