Question

1. Question • According to the law of definite proportions a) if the same two elements form two different compounds, they do so in the same ratio. b) it is not possible for the same two elements to form more than one compound. c) the ratio of the masses of the elements in a compound is always the same. d) the total mass after a chemical change is the same as before the change.

2. Answer • c) the ratio of the masses of the elements in a compound is always the same. • This describes the result of elements combining to form compounds.

3. Question • Ernest Rutherford • a) determined the charge of a single electron. • b) proposed that cathode rays contained electrons. • c) determined the existence of neutrons. • d) conducted the “gold foil” experiment.

4. Answer • d) conducted the “gold foil” experiment. • Robert Millikan determined the charge of a single electron. J.J. Thomson proposed the “plum pudding” model of the atom. James Chadwick determined the existence of neutrons.

5. Question • How many of the following did Dalton notdiscuss in his atomic theory? • I. Isotopes • II. Ions • III. Protons • IV. Neutrons • V. Electrons • a) One b) Two c) Three d) Four e) Five

6. Answer • e) Five • Dalton only addressed matter’s basic unit as atoms in his theory.

7. Question • The element Rhenium (Re) exists as two stable isotopes and 18 unstable isotopes. Rhenium-185 isotope has in its nucleus a) 75 protons and 75 neutrons. b) 75 protons and 130 neutrons. c) 130 protons and 75 neutrons. d) 75 protons and 110 neutrons.

8. Answer • d) 75 protons and 110 neutrons. • The mass number is the sum of the protons (same as the atomic number) and neutrons.

9. Question • Which of the following statements are true? • I. The number of protons is the same for all • neutral atoms of an element. • II. The number of electrons is the same for all neutral atoms of an element. • III. The number of neutrons is the same for all neutral atoms of an element. a) I, II, and III are all true. b) Only I and II are true. c) Only II and III are true. d) Only I and III are true. e) I, II, and III are all false.

10. Answer • b) Only I and II are true. • For neutral atoms of an element, the number of protons equals the number of electrons and is the same as the atomic number. However, the number of neutrons differs depending on the isotopes.

11. Question • Boron (B) has two isotopes: B with mass of • 10.013 amu and B with mass of 11.009 amu. • The average atomic mass of boron is 10.81 • amu. The fractional abundance of each isotope • is a) 0.990 of Boron-10 and 0.010 of Boron-11. b) 0.804 of Boron-10 and 0.196 of Boron-11. c) 0.500 of Boron-10 and 0.500 of Boron-11. d) 0.196 of Boron-10 and 0.804 of Boron-11. e) 0.010 of Boron-10 and 0.990 of Boron-11.

12. Answer • d) 0.196 of Boron-10 and 0.804 of Boron-11. • Since the average atomic mass is closer to that of Boron-11, the fractional abundance of Boron-11 must be higher than that of Boron-10. The average atom mass is significantly less than that of Boron-11, so there is a significant fractional abundance of Boron-10. • (10.013 amu × 0.196) + (11.009 amu × 0.804) = 10.81 amu

13. Question • An ion is formed a) by either adding or subtracting protons from the atom. b) by either adding or subtracting electrons from the atom. c) by either adding or subtracting neutrons from the atom. d) All of the above can form an ion. e) Two of the above can form an ion.

14. Answer • b) by either adding or subtracting electrons from the atom. • The atoms of an element form ions when electrons are gained or lost.

15. Question • What is the wavelength (in nm) of electromagnetic radiation that has a frequency of 7.45 × 1014/s? • (Hint: c = 3.00 × 108 m/s and h = 6.63 × 10−34 J.s) a) 4.03 × 10−7 nm b) 403 nm c) 4.03 nm d) 2.24 × 1014 nm e) 1.34 × 10−6 nm

16. Answer • b) 403 nm • For all electromagnetic radiation c = . So, • Be sure to convert to the desired units.

17. Question • Which form of electromagnetic radiation has the shortest wavelengths? a) Gamma rays b) Microwaves c) Radio waves d) Infrared radiation e) X-rays

18. Answer • a) Gamma rays • The radiation with the shortest wavelength is of highest energy.

19. Question • Which form of electromagnetic radiation has the lowest energy? a) Red light b) Yellow light c) Blue light d) All visible light has the same energy.

20. Answer • a) Red light • Red light is closest to the infrared region and so it has the lowest energy.

21. Question • Which form of electromagnetic radiation has the shortest wavelength? a) Red light b) Yellow light c) Blue light d) All visible light has the same wavelength.

22. Answer • c) Blue light • The radiation with the shortest wavelength is of highest energy. Blue light is closest to ultraviolet light.

23. Question • Which form of electromagnetic radiation has the lowest frequency? a) Red light b) Yellow light c) Blue light d) All visible light has the same frequency.

24. Answer • a) Red light • The radiation with the lowest frequency has the lowest energy.

25. Question • Which form of electromagnetic radiation has the slowest speed? a) Red light b) Yellow light c) Blue light d) All visible light has the same speed.

26. Answer • d) All visible light has the same speed. • All electromagnetic radiation, which includes visible light, has the same speed ~3.00 × 108 m/s.

27. Question • The photoelectric effect predicts that a) electrons can be ejected from the surface of a metal using a vacuum. b) electrons can be ejected from the surface of a metal using light with a frequency greater than a certain threshold value. c) electrons can be ejected from the surface of a metal using light with a frequency less than a certain value. d) electrons can be ejected from the surface of a metal using light with a frequency greater than a certain threshold value that is the same for all metals.

28. Answer • b) electrons can be ejected from the surface of • a metal using light with a frequency greater • than a certain threshold value. • The photoelectric effect predicts that electrons can be ejected from the surface of a metal using light with a frequency greater than a certain threshold value. The threshold value is characteristic of the metal.

29. Question • From the following list of observations, choose the one that most clearly supports the following conclusion: • Electrons have wave properties. a) Emission spectrum of hydrogen b) The photoelectric effect c) Scattering of alpha particles by metal foil d) Diffraction e) Cathode “rays”

30. Answer • d) Diffraction • Diffraction patterns are produced by waves.

31. Question • From the following list of observations, choose the one that most clearly supports the following conclusion: • Electrons in atoms have quantized energies. a) Emission spectrum of hydrogen b) The photoelectric effect c) Scattering of alpha particles by metal foil d) Diffraction e) Cathode “rays”

32. Answer • a) Emission spectrum of hydrogen • The emission spectrum shows only certain colors of light, providing support for quantized energy levels.

33. Question • Which of the following statements is false? a) The energy of electromagnetic radiation increases as its frequency increases. b) An excited atom can return to its ground state by absorbing electromagnetic radiation. c) An electron in the n = 4 state in the hydrogen atom can go to the n = 2 state by emitting electromagnetic radiation at the appropriate frequency. d) The frequency and wavelength of electromagnetic radiation are inversely proportional to each other.

34. Answer • b) An excited atom can return to its ground state by absorbing electromagnetic radiation. • An excited atom returns to its ground state by releasing energy in the form of electromagnetic radiation.

35. Question • For which of the following electron transitions for a hydrogen atom does the light emitted have the longest wavelength? a) n = 4 to n = 3 b) n = 4 to n = 2 c) n = 4 to n = 1 d) n = 3 to n = 2 e) n = 2 to n = 1

36. Answer • a) n = 4 to n = 3 • Energy is inversely related to wavelength, so the smaller the energy change, the longer the wavelength. The transition n = 4 to n = 3 has the smallest energy change of all of the options.

37. Question • The quantum number n a) can have the value of any integer. b) distinguishes orbitals with different shapes. c) is known as the principal quantum number. d) refers to the orientation of the spin axis of the electron.

38. Answer • c) is known as the principal quantum number. • The principal quantum number is n and can have only positive integer values of 1, 2, 3, and so on. The quantum number l distinguishes orbitals with different shapes. The quantum number ms refers to the orientation of the spin axis of the electron.

39. Question • If the l quantum number is 3, what are the possible values of ml ? a) 3, 2, 1 b) 3, 2, 1, 0 c) 3, 2, 1, 0, −1, −2, −3 d) 2, 1 e) 2, 1, 0 f) 2, 1, 0, −1, −2

40. Answer • c) 3, 2, 1, 0, −1, −2, −3 • The allowed values for ml are the integers between −l and l.

41. Question • What is the subshell notation when n = 3, and l = 2? a) 3s b) 3p c) 3d d) 3f

42. Answer • c) 3d • The subshell notation includes the principal quantum number n followed by the letter designation for the orbital type (l = 0 is denoted by s;l = 1 is denoted by p;l = 2 is denoted by d; and l = 3 is denoted by f).

43. Question • A ground state electron in the hydrogen atom is given just enough energy to get to n = 2. Which orbital will the electron occupy? a) The 2s orbital b) The 2px orbital c) The 2py orbital d) The 2pz orbital e) Each of the above is equally likely.

44. Answer • e) Each of the above is equally likely. • Because the hydrogen atom has only one electron, the 2s and 2p orbitals are degenerate (have the same energy).

45. Question • Which of the following combinations of quantum numbers is not allowed? • nlmlms a) 1 1 0 ½ b) 3 0 0 −½ c) 2 1 −1 ½ d) 4 3 −2 −½ e) 4 2 0 ½

46. Answer • a) 1 1 0 ½ • Electrons with n = 1 can only have values for l of 0.

47. Question • How many electrons can be described by the quantum numbers n = 3, l = 3, ml = 1? a) 0 b) 1 c) 2 d) 6 e) 10 f) 14

48. Answer • a) 0 • Electrons with n = 3 can only have values for l of 0, 1, or 2.

49. Question • How many electrons can be described by the quantum numbers n = 3, l = 2, ml = −1? a) 0 b) 1 c) 2 d) 6 e) 10 f) 14

50. Answer • c) 2 • Electrons with n = 3 can have values for l of 0, 1, or 2. Electrons with l = 2 can have values for ml of −2, −1, 0, 1, or 2. Thus, n = 3, l = 2, ml = −1 is allowed. Since ml can be +1/2 or −1/2, two electrons can share these values of n, l, and ml .