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Chemistry Assignments Ch 4 Atomic Structure pg 103 4) all matter is composed of atoms atoms of different elements differ chemical change involves a rearrangements of atoms 5) Atoms of one element are never changed into atoms of another element as a result of a chemical change 6) 5 x 10-2 nm to 2 x 10-1 nm 7) 1.05 x 10-22 g pg 102 Atoms are separated, joined, or rearranged. pg 105 Checkpoint: A negatively charged plate repels a cathode ray. pg 108 10) proton—positive charge, relative mass = 1 electron—negative charge, relative mass = 1/1840 neutron—no charge, relative mass = 1 11) Thomson passed an electric current through sealed glass tubes filled with gases The resulting glowing beam consisted of tiny negatively charged particles moving at high speed. Thomson concluded that electrons must be parts of the atoms of all elements. Millikan determined the charge and mass of the electron. 12) Rutherford expected all the alpha particles to pass straight through, but some particles were deflected at very large angles—and some even bounced straight back. 13) The great majority of the alpha particles passed straight through the gold foil. 14) Rutherford’s atomic model described the atom as having a positively charged, dense nucleus that is tiny compared to the atom as a whole. In Thomson’s plum pudding model, electrons were stuck in a chunk of positive charge. pg 111 Checkpoint: Mass number = number of neutrons + atomic number 15) a) 19 b) B c) 5 d) 5 e) 16 f)16 16) a) 9 protons and 9 electrons b) 20 protons and 20 electrons c) 13 protons and 13 electrons pg 112 17) a) 8 b) 16 c) 61 d) 45 e) 125 g)23 h) 23 18) a) C, mass number = 12, atomic number = 6 b) F, mass number = 19, atomic number = 9 c) Be, mass number = 9, atomic number = 4 pg 113 Checkpoint: hydrogen-1, hydrogen-2, hydrogen-3 19) oxygen, O with atomic number 8 and mass numbers 16, 17, 18 20) Chromium-50 has 26 neutrons Chromium-52 has 28 neutrons Chromium 53 has 29 neutrons pg 111 Checkpoint: Add the number of neutrons and number of protons (atomic number) pg 113 Checkpoint: hydrogen-1 (protium), hydrogen-2 (deuterium), hydrogen-3 (tritium) pg 116 Checkpoint: The number of stable isotopes, the mass of each isotope, and the natural abundance (expressed as a percent) of each isotope. pg 117 23) 63.6 amu 24) 79.91 amu pg 119 30) 194 represents the mass number 31) The atomic mass is the weighted average of the masses of its isotopes 32) a) lithium-6: 3p+, 3e-, 3no; lithium-7: 3p+, 3e-, 4no; b) calcium-42: 20p+, 20e-, 22no; calcium-44: 20p+, 20e-, 24no; c) selenium-78: 34p+, 34e-, 44no; selenium-80: 34p+, 34e-, 46no; 33) any two: beryllium (Be), magnesium (Mg), strontium (Sr), barium (Ba), radium (Ra) Elements Handbook: oxygen (Period2, Group 6A) carbon (Period 2, Group 4A) hydrogen (Period 1, Group 1A) nitrogen (Period 2, Group 5A) calcium (Period 4, Group 2A) pg 122 35) Democritus’ ideas were not helpful in explaining chemical behavior because they lacked experimental support. 36) Dalton would agree with all four statements because they all fit his atomic theory. 38) a) A beam of electrons (cathode rays) is deflected by an electric field toward the positively charged plate. b) The cathode rays were always composed of electrons regardless of the metal used in the electrodes or the gas used in the cathode-ray tube. 39) repel 40) The mass of the proton and neutron are equal; protons are positively charged and neutrons are neutral. 42) The electrons were stuck in a lump of positive charge. 44) positive 45) protons and neutrons (Rutherford suspected there was something in the nucleus in addition to protons—but didn’t know them as neutrons) 46) It has equal numbers of protons and electrons. 48) a) 15 b) 42 c) 13 d) 48 e) 24 f) 82 50) a) 19 b) 9 c) F d) 14 e) 29 f) Si h) 22 i) Ti j) 25 k) 30 l) Mn g) 22 52) because of the existence of isotopes 61) All atoms of the same elements are not identical (isotopes). The atoms is not the smallest particle of matter. 68) a) 92.90 % b) 99.89% c) .00993% 72) Because they have identical numbers of protons, they also have identical numbers of electrons; electrons are the subatomic particles that are responsible for chemical behavior. pg 125 1) C 2) A 3) B 4) B 5) 9; three Ca-42 atoms have an approximate mass of 3 x 42- 126 amu; one N-14 atoms has an approximate mass of 145 amu; 126/14 = 9 N-14 atoms with an approximate mass of 126 amu. 6) E 7) false, true 8) true, false 9) true, true, correct explanation