Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 4 Assignment Answers 34. An atom is the smallest particle of an element that has the properties of that element. 36. Dalton would agree with all 4 statements. 38. a. Since the cathode rays traveled towards the positive terminal of the CRT, and were deflected by magnets and charged plates he knew they were (-) charged. b. Thomson observed the same cathode rays with all of the different metals that he used. 39. Two electrons should repel each other. 40. The mass of a neutron is equal to the mass of a proton: 1 amu. However a proton is (+) charged and a neutron is neutral. 41. When an atom loses electrons, there are now more protons than electrons – therefore the atom has an overall positive charge. 42. In Thomson’s “plum pudding” model, the electrons are scattered among a “blob” of positivity. 43. Rutherford was shocked to see the alpha particles scattered at large angles, even reflected right back at him. This would not be expected with Thomson’s model of the atom. 44. The nucleus of every atom has a (+) charge, with the magnitude of the charge being equal to the number of protons. 45. In Rutherford’s model, the nucleus contained protons and some other particle that Rutherford suspected was there (but he had no direct evidence of the neutron). 46. The atom is electrically neutral because it contains equal numbers of protons and electrons. 47. The atomic number (Z) is the number of protons in the nucleus. 48. a. 15 b. 42 c. 13 d. 48 e. 24 f. 82 49. The mass number (A) is protons plus neutrons. The atomic number (Z) is the number of protons only. 50. Atomic number Mass number Protons Neutrons Symbol 9 a. 19 b. 9 10 c. F d. 14 14 15 f. Si g. 22 e. 29 47 h. 22 25 i. Ti j. 25 55 25 k. 30 l. Mn 51. Isotopes of an element are different in their mass numbers, number of neutrons, relative abundance, and individual masses. 52. Each element has more than 1 different isotope, so there are a greater number of atoms than there are elements. 53. To calculate the atomic mass of an element, you have to know the relative abundances of the isotopes as well as their individual masses. 54. A weighted average mass takes into account percent abundances of the isotopes. This is the way chemists define atomic masses. 55. The atomic mass of an element is the weighted average of the masses of the isotopes of that element. 56. On the periodic table, elements are arranged according to their atomic numbers. They are arranged in increasing order. 59. The size of the nucleus is very small compared to the size of the overall atom, yet the atom’s mass is found primarily in the nucleus of the atom. So the nucleus is very dense, while the atom overall is not very dense. 60. Standing on top of a boron-11 nucleus, you would see 5 protons and 6 neutrons in the nucleus, and 5 electrons outside the nucleus. 65. atomic mass of lead = (0.014 x 204 amu) + (0.241 x 206 amu) + (0.221 x 207 amu) + (0.524 x 208 amu) = 207.241 amu 69. atomic mass of nitrogen = (0.9963 x 14.003 amu) + (0.0037 x 15.000 amu) = 14.007 amu 71. The atomic number is the number of protons. The number of electrons is equal to the number of protons (in the neutral atom). The mass number minus the atomic number is equal to the number of neutrons. 72. Because isotopes have the same number of protons, and therefore electrons, they behave the same chemically. Chemical behavior is governed by the number of valence electrons in the atom.