1. All matter is composed of atoms; atoms of the same element are the same, and atoms of different elements are different; atoms combine in whole-number ratios to form compounds. 3. a. Sodium---alkali metal b. Magnesium---Alkaline earth metal c. Calcium---Alkaline earth metal d. Chlorine---halogen e. Potassium---Alkali metal 5. Most of the alpha particles went through the metal sheet because atoms are mostly empty space. 7. Electrons are in orbit about the nucleus. 9. The electron weighs the least. The protons and neutrons are found in the nucleus while electrons are located outside the nucleus. 11. Proton, electron 13. Least, outside 15. a. Z = 8; O; atomic oxygen b. Z = 27; Co; cobalt c. Z = 33; As; arsenic e. Z = 90; Th; thorium 17. a. P b. Mo c. Be 19. a. Ag b. S c. N d. Ne 21. a. 86 b. 74 c. 24 d. 4 23. Column 1 is the alkali metals. Column 2 is the alkaline earth metals. Columns 3 - 12 are the transition metals. 25. The transition metals can exist in more than one charge state. They have variable charge. 27. Calcium and Barium (belong to same group). 29. Magnesium; Beryllium 31. Helium; Xenon; Neon 33. metal; transition metal. 35. a,d 37. a. 1A (1) b. 1A (1) c. 8A (18) d. 6A (16) 39. 0 1 2 3 Chemical Symbol Group Number Group Name Metal or Non-metal Br 7A (17) Halogens Non-metal Sr 2A (2) Alkaline earth metals metal Ne 8A (18) Noble gases Non-metal K 1A (1) Alkali metal metal 41. a and d 43. a and b 45. a. 27 b. 38 c. 54 d. 28 47. a. 10 b. 2 c. 46 d. 30 49. a. Li, Li + , 2nd period, group 1 b. F, F – , 2nd period, group 17 c. Al, Al 3+ , 3nd period, group 13 51. a. 2 b. 3 c. 3 d. 1 53. a. 1+ b. 2− c. 2+, 3+ 55. SO 3 is sulfur trioxide, while SO 3 2− is the sulfite ion. 57. All isotopes of nitrogen have the same atomic number (Z = 7). Yes, all isotopes of the same element have the same Z. 59. a. Z=1, A=3 b. Z=20, A=42 c. Z=73, A=182 d. Z=24, A=52 61. a. 26 b. 22 c. 2 63. a. b. c. d. e. 65. a. protons=43; neutrons=54; electrons=43 b. protons=49; neutrons=64; electrons=49 c. protons=28; neutrons=35; electrons=28 d. protons=26; neutrons=29; electrons=26 67. a. protons=82; neutrons=125; electrons=82 b. protons=8; neutrons=8; electrons=8 c. protons=55; neutrons=82; electrons=55 d. protons=19; neutrons=21; electrons=19 69. This iron atom has 26 protons and 56 − 26 = 30 neutrons. 71. a. He b. B c. Bi & P 73. 0 1 2 3 Number of protons Number of neutrons Element name Isotope Symbol 80 120 Mercury NaN 26 29 iron NaN 1 2 Hydrogen NaN 75. If "CO" was written as the chemical symbol for cobalt, it would be the same as the chemical formula for carbon monoxide. This ambiguity would create a lot problems such as in labeling and might lead to life-threatening danger. And The chemical symbol is ALWAYS written with the first letter in uppercase and the second letter in lowercase. 77. a) Iron, 26 protons, 24 electrons, and 32 neutrons; (b) iodine, 53 protons, 54 electrons, and 74 neutrons 79. If the atomic number of uranium is 92, then that is the number of protons in the nucleus. Because the mass number is 235, then the number of neutrons in the nucleus is 235 − 92, or 143.