Answers to Questions & Problems in Textbook - Chapter 3

1. Although the number and nature of the elementary substances postulated by the ancient Greeks were incorrect, their idea that the matter we encounter in everyday life is composed of a few simpler substances is very similar to our modern concepts. Also, the idea that the simpler substances combine with each other in regular, fixed manners compares well with the modern theory of matter.
2. in your text and most importantly, alchemists were doing experiments which were increasing the entire body of scientific knowledge.
3. Boyle's most important contribution was his insistence that science should be firmly grounded in experiment. Boyle tried to limit the influence of any preconceptions about science, and only accepted as fact what could be demonstrated.
4. in your text
5. Oxygen is found in great abundance in the oceans (combined with hydrogen in water molecules) and in the earth itself (most rocks and minerals are compounds that contain oxygen). Oxygen is found more commonly in compounds than alone as an element.
6. in your text
7. B(boron), C(carbon) F(fluorine), H(hydrogen), I(iodine), K(potassium), N(nitrogen), O(oxygen), P(phosphorous), S(sulfur), U(uranium), V(vanadium), W(tungsten), Y(yttrium).
8. in your text
9.
  1. in your text
  2. Ni
  3. in your text
  4. Si
  5. in your text
  6. Ag
10. Fe, Iron. Cl, chlorine. S, sulfur. U, uranium. Ne, neon. K, pottasium.
11.
  1. in your text
  2. Cobalt
  3. in your text
  4. Carbon
  5. in your text
  6. Cesium
  7. in your text
  8. Cadium
12.
  1. False; most materials occur as mixtures of compounds
  2. False; a given compound always contains the same relative number of atoms of its various elements. The ratio of the number of atoms is always the same; i.e. it way be a drop of water with less total atoms, but still in the ratio of 2-H to 1-O, or it could be a lake of water which would still be the 2:1 ratio, yet it would obviously be far more total number of atoms.
  3. False; molecules are made up of tiny particles called atoms.
13. in your text - no need to give specific examples until after we do the LAD 3
14. A compound is a pure substance that is composed of two or more elements chemically combined and always contains exactly the same relative masses of those elements.
15. in your text
16.
  1. in your text
  2. B2H6
  3. in your text
  4. CBr4
  5. in your text
  6. H3PO4
17.
  1. False; Thomson obtained identical beams, presumably made of of identical particles, whose nature did not depend on what gas was used to generate them.
  2. true
  3. False; At first the atom was envisioned as a sphere of positive charge in which negatively charged electrons were randomly distributed. We often describe it as spherical area where the positively charged protons and the negatively charged electrons are evenly distributed.
18. in your text
19. neutrons
20. in your text
21. The proton and the neutron have very similar (but not identical) masses. Either of these particles has a mass approximately 2000 times greater than that of an electron. The combination of the protons and the neutrons make up the bulk of the mass of the atom, but the electrons make the greatest contribution to the size and the chemical properties of the atom.
22. in your text
23. False; atoms that have the same number of protons, with different numbers of neutrons, represent isotopes. Isotopes are atoms of the same element, which therefore must have the same number of protons, but its the number of neutrons that can vary.
24. in your text. The mass number represents the sum of the protons plus the neutrons.
25. Dalton's original theory proposed that all atoms of a given element were identical. We now realize that different atoms of the same element must have a particular number of protons and electrons (the atomic number), but may have different numbers of neutrons (leading to different mass numbers). These would of course be isotopes.
26. in your text
27.
  1. in your text
  2. 30
  3. in your text
  4. 74
  5. 38
  6. 27
  7. in your text
  8. 3
28.
  1. in your text
  2. 3717Cl
  3. in your text
  4. 5726Fe
  5. in your text
  6. 73Li
29.
  1. in your text
  2. 95 protons, 146 neutrons, 95 electrons
  3. in your text
  4. 55 protons, 78 neutrons, 55 electrons
  5. in your text
  6. 25 protons, 31 neutrons, 25 electrons
30.
  1. sodium: 2311Na, atomic number 11, mass number 23, number of neutrons 12
  2. nitrogen: 157N, atomic number 7, mass number 15, number of neutrons 8
  3. barium: 13656Ba, atomic number 56, mass number 136, number of neutrons 80
  4. lithium: 93Li, atomic number 3, mass number 9, number of neutrons 6
  5. boron: 115B, atomic number 5, mass number 11, number of neutrons 6
31. The elements are listed in the periodic table in order of increasing atomic number (number of protons in the nucleus). Left to right then down. Elements with similar chemical properties are arranged in the columns. The periodic table originally was arranged on the basis of mass.
32. in your text
33. Metals are excellent conductors of heat and electricity, and are malleable, ductile, and generally shiny (lustrous) when a fresh surface is exposed.
34. in your text
35. Merucry is a liquid at room temperature.
36. in your text
37. The only metal which ordinarily occurs as a liquid is mercury. The only nonmetallic elements which occurs as a liquid at room temperature is bromine (elements such as oxygen and nitrogen are frequently obtainable as liquids, but these result from compression of the gases into cylinders at very low temperatures).
38. in your text
39.
  1. in your text
  2. Group 2; alkaline earth elements
  3. in your text
  4. Group 1; alkali metals
  5. in your text
  6. Group 1; alkali metals
  7. in your text
40.
  1. in your text
  2. germanium: Ge, atomic number 32, group number 4, metalloid
  3. in your text
  4. titanium: Ti, atomic number 22, no group number, transition metal
  5. iodine: I, atomic number 53, group number 7, nonmetal
41. Most of the elements are too reactive to be found in the uncombined form in nature, and are found only in compounds.
42. in your text
43. Diatomic gases: H2, N2, O2, Cl2, F2, (Br2, I2, are liquid and solid at room conditions, but they are diatomic and easily converted to gases.) Monatomic gases: He, Ne, Kr, Xe, Rn, and Ar
44. in your text
45. 1-b, 2-d, 3-b, 4-h, 5-f, 6-e, 7-a, 8-c, 9-g, 10-i
46.
  1. in your text
  2. Co2+: 27 protons, 24 electrons, Co2O,sub.3
  3. in your text
  4. K+: 19 protons, 18 electrons, K2O
  5. in your text
  6. Sr2+: 38 protons, 36 electrons, SrO
  7. in your text
  8. P3-: 15 protons, 18 electrons, Ca3P2
47.
  1. in your text
  2. P: 15 protons, 15 electrons. P3-: 15 protons, 18 electrons
  3. in your text
  4. Fe: 26 protons, 26 electrons. Fe3+: 26 protons, 23 electrons
  5. in your text
  6. N: 7 protons, 7 electrons. N3-: 7 protons, 10 electrons
48.
  1. in your text
  2. Sr2+
  3. in your text
  4. Ra2+
  5. in your text
  6. Al3+
49. A compound which has a high melting point(many hundreds of degrees) and which conducts an electrical current when melted or dissolved in water almost certainly consists of ions.
50. In rhe solid state, although ions are present, they are rigidly held in fixed positions in the crystal of the substance. In order for ionic substances to be able to pass an electrical current, the ions must be able to move, which is possible when the solid is converted to the liquid state.
51. in your text
52.
  1. in your text
  2. The smallest common multiple of 3 and 2 is 6; three 2- ions are required to balance two 3+ ions: Fe2S3
  3. in your text
  4. Two 1- ions are required to balance one 3+ ion: FeCl3
  5. in your text
  6. The smallest common multiple of 2 and 3 is 6; two 3- ions are required to balance three 2+ ions: Mg3N2
  7. in your text
  8. Two 1+ ions are required to balance one 2- ion: Na2S
53. The atomic number represents the number of protons in the nucleus of an atom. The mass number represents the total number of protons and neutrons. No two different elements have the same atomic number. Yet if the total number of protons and neutrons happens to be the same for two isotopes of different elements, then the atoms will have the same mass number, although they would have different atomic numbers.
54. in your text
55. Yes. For example, carbon and oxygen form carbon monoxide (CO) and carbon dioxide (CO2). The existence of more than one compound between the same elements does not in any way contradict Dalton's theory. For example, the relative mass of carbon in different samples of CO is always the same, and the relative mass of carbon in different samples of CO2 is also always the same. Dalton did not say, however, that two different compounds would have to have the same relative masses of the elements present. In fact, Dalton said that two different compounds of the same elements would have to have different relative masses of the elements.
56.
  1. in your text
  2. AlCl3
  3. in your text
  4. SCl6