Download Chapter 4 Assignment Answers

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 = 207.241 amu
69. atomic mass of nitrogen = 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.