Chapter 2

# Chapter 2 - CHAPTER 2 ATOMS, MOLECULES, AND IONS 2.7 First,...

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CHAPTER 2 ATOMS, MOLECULES, AND IONS 2.7 First, convert 1 cm to picometers. 10 12 0.01 m 1 pm 1 cm 1 10 pm 1cm 11 0 m ×× = × × 10 2 1Heatom (1 10 pm) 0p m × = × 8 ? He atoms 1 10 He atoms × 2.8 Note that you are given information to set up the unit factor relating meters and miles. 44 nucleus 1m 1mi 10 10 10 cm 100 cm 1609 m == × × × = atom 0.62 mi r r 2.11 For iron, the atomic number Z is 26. Therefore the mass number A is: A = 26 + 28 = 54 2.12 Strategy: The 239 in Pu-239 is the mass number. The mass number ( A ) is the total number of neutrons and protons present in the nucleus of an atom of an element. You can look up the atomic number (number of protons) on the periodic table. Solution: mass number = number of protons + number of neutrons number of neutrons = mass number number of protons = 239 94 = 145 2.13 Isotope 2 3 He 2 4 12 24 Mg 12 25 22 48 Ti 35 79 Br 78 195 Pt No. Protons 2 2 12 12 22 35 78 No. Neutrons 1 2 12 13 26 44 117 2.14 Isotope 7 15 N 16 33 S 29 63 Cu 38 84 Sr 56 130 Ba 74 186 W 80 202 Hg No. Protons 7 16 29 38 56 74 80 No. Neutrons 8 17 34 46 74 112 122 No. Electrons 7 16 29 38 56 74 80 2.15 (a) 11 23 Na (b) 28 64 Ni 2.16 The accepted way to denote the atomic number and mass number of an element X is as follows: Z A X where, A = mass number Z = atomic number (a) 74 186 (b) 80 201

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CHAPTER 2: ATOMS, MOLECULES, AND IONS 21 2.21 Helium and Selenium are nonmetals whose name ends with ium . (Tellerium is a metalloid whose name ends in ium .) 2.22 (a) Metallic character increases as you progress down a group of the periodic table. For example, moving down Group 4A, the nonmetal carbon is at the top and the metal lead is at the bottom of the group. (b) Metallic character decreases from the left side of the table (where the metals are located) to the right side of the table (where the nonmetals are located). 2.23 The following data were measured at 20 ° C. (a) Li (0.53 g/cm 3 ) K (0.86 g/cm 3 ) H 2 O (0.98 g/cm 3 ) (b) Au (19.3 g/cm 3 ) Pt (21.4 g/cm 3 ) Hg (13.6 g/cm 3 ) (c) Os (22.6 g/cm 3 ) (d) Te (6.24 g/cm 3 ) 2.24 F and Cl are Group 7A elements; they should have similar chemical properties. Na and K are both Group 1A elements; they should have similar chemical properties. P and N are both Group 5A elements; they should have similar chemical properties. 2.29 (a) This is a polyatomic molecule that is an elemental form of the substance. It is not a compound. (b) This is a polyatomic molecule that is a compound. (c) This is a diatomic molecule that is a compound. 2.30 (a) This is a diatomic molecule that is a compound. (b) This is a polyatomic molecule that is a compound. (c) This is a polyatomic molecule that is the elemental form of the substance. It is not a compound. 2.31 Elements: N 2 , S 8 , H 2 Compounds: NH 3 , NO, CO, CO 2 , SO 2 2.32 There are more than two correct answers for each part of the problem. (a) H 2 and F 2 (b) HCl and CO (c) S 8 and P 4 (d) H 2 O and C 12 H 22 O 11 (sucrose) 2.33 Ion Na + Ca 2 + Al 3 + Fe 2 + I F S 2 O 2 N 3 No. protons 11 20 13 26 53 9 16 8 7 No. electrons 10 18 10 24 54 10 18 10 10 2.34 The atomic number ( Z ) is the number of protons in the nucleus of each atom of an element. You can find this on a periodic table. The number of electrons in an ion is equal to the number of protons minus the charge on the ion.
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## This note was uploaded on 10/11/2009 for the course CHE 102 taught by Professor Maggie during the Fall '09 term at Wisc Whitewater.

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Chapter 2 - CHAPTER 2 ATOMS, MOLECULES, AND IONS 2.7 First,...

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