Chapter 2

Explain how the results of the gold-foil experiment led Rutherford to dismiss the plum-pudding model of the atom and create his own model based on a nucleus surrounded by electrons.

Had the plum-pudding model been valid, how would the results of the gold-foil experiment have differed from what Geiger and Marsden actually observed?

What properties of cathode rays led Thomson to conclude that they were not rays of energy but rather particles with an electric charge?

Describe two ways in which \(\alpha\) particles and \(\beta\) particles differ.

How might using a thicker piece of gold foil have affected the scattering pattern of \(\alpha\) particles observed by Rutherford's students?

In addition to gold foil, Geiger and Marsden tried silver and aluminum foils in their experiment. Why might foils of these metals have deflected fewer \(\alpha\) particles than gold foil?

If the mass number of a nuclide is more than twice the atomic number, is the neutron-to-proton ratio less than, greater than, or equal to \(1 ?\)

How are the mass number and atomic number of a nuclide related to the number of neutrons and protons in each of its nuclei?

Nearly all stable nuclides have at least as many neutrons as protons in their nuclei. Which very common nuclide is an exception?

Explain the inherent redundancy in the nuclide symbol $$_{Z}^{A} \mathrm{X}$$

How many protons, neutrons, and electrons are in the following atoms? (a) \(^{14} \mathrm{C} ;\) (b) \(^{59} \mathrm{Fe} ;\) (c) \(^{90} \mathrm{Sr} ;\) (d) \(^{210} \mathrm{Pb}\)

How many protons, neutrons, and electrons are there in the following atoms? (a) \(^{11} \mathrm{B} ;\) (b) \(^{19} \mathrm{F} ;\) (c) \(^{131} \mathrm{I}\); (d) \(^{222} \mathrm{Rn}\)

Calculate the ratio of neutrons to protons in the following stable atomic nuclei: (a) \(^{4} \mathrm{He} ;\) (b) \(^{23} \mathrm{Na} ;\) (c) \(^{59} \mathrm{Co} ;\) and (d) \(^{197}\) Au. Each of these elements exists naturally as a single isotope. What trend do you observe for the neutronto-proton ratio as \(Z\) increases?

Calculate the ratio of neutrons to protons in the following group 15 nuclei: (a) \(^{14} \mathrm{N} ;\) (b) \(^{31} \mathrm{P} ;\) (c) \(^{75} \mathrm{As} ;\) (d) \(^{121} \mathrm{Sb} ;\) and (e) \(^{123}\) Sb. How does the ratio change with increasing atomic number?

Mendeleev arranged the elements on the left side of his periodic table based on the formulas of the binary compounds they formed with oxygen, and he used the formulas as column labels. For example, group 1 in a modern periodic table was labeled "R \(_{2} \mathrm{O} "\) in Mendeleev's table, where "R" represented one of the elements in the group. What labels did Mendeleev use for groups \(2,3,\) and 4 from the modern periodic table?

Mendeleev arranged the elements on the right side of his periodic table based on the formulas of the binary compounds they formed with hydrogen and used these formulas as column labels. Which groups in the modern periodic table were labeled "\(\mathrm{HR}," "\mathrm{H}\) \(_{2} \mathrm{R},\) " and "\(\mathrm{H}\) \(_{3} \mathrm{R},\) " where "\(\mathrm{R}\)" represented one of the elements in the group?

Mendeleev left empty spaces in his periodic table for elements he suspected existed but had yet to be discovered. However, he left no spaces for the noble gases (group 18 in the modern periodic table). Suggest a reason why he left no spaces for them.

Describe how the charges of the monatomic ions that elements form change as group number increases in a particular row of the periodic table and how ion charges change as the row number increases in a particular group.

TNT Molecules of the explosive TNT contain atoms of hydrogen and second-row elements in groups \(14,15,\) and 16. Which three elements are they?

Phosgene was used as a chemical weapon during World War I. Despite the name, phosgene molecules contain no atoms of phosphorus. Instead, they contain atoms of carbon and the group 16 element in the second row of the periodic table and the group 17 element in the third row. What are the identities and atomic numbers of the two elements?

The catalytic converters used to remove pollutants from automobile exhaust contain compounds of several fairly expensive elements, including those described in the following list. Which elements are they? a. The group 10 transition metal in the fifth row of the periodic table b. The transition metal whose symbol is to the left of your answer to part a c. The transition metal whose symbol is directly below your answer to part a

Compounds containing chlorine have long been used to disinfect the water in swimming pools, but in recent years a compound of a less corrosive halogen has become a popular alternative disinfectant. What is the name of this fourth-row element?

How many metallic elements are there in the third row of the periodic table?

What is meant by a weighted average?

Explain how percent natural abundances are used to calculate average atomic masses.

In calculating the formula masses of binary ionic compounds, we use the average masses of neutral atoms, not ions. Why?

The average mass of platinum is 195.08 amu, yet the natural abundance of \(^{195} \mathrm{Pt}\) is only \(33.8 \% .\) Propose an explanation for this observation.

The argon in nature consists of three isotopes: \(^{36} \mathrm{Ar},^{38} \mathrm{Ar}\) and \(^{40}\) Ar. Which one is the most abundant?

Manganese has only one stable isotope. How many neutrons are in each of its atoms?

Copper in nature is a mixture of \(69.17 \%\) copper- 63 \((62.9296 \text { amul })\) and \(30.83 \%\) copper \(-65(64.9278 \text { amu }) .\) Use this information to calculate the average atomic mass of copper.

Sulfur in nature is a mixture of four isotopes: \(^{32} \mathrm{S}\) \((31.9721 \mathrm{amu}, 95.04 \%) ;^{33} \mathrm{S}(32.9715 \mathrm{amu}, 0.75 \%) ;^{34} \mathrm{S}\) \((33.9679 \mathrm{amu}, 4.20 \%) ;\) and \(^{36} \mathrm{S}(35.9671 \mathrm{amu}, 0.01 \%) .\) Use this information to calculate the average atomic mass of sulfur.

The natural abundances of the four isotopes of strontium are \(0.56 \%^{84} \mathrm{Sr}(83.9134 \mathrm{amu}), 9.86 \%^{86} \mathrm{Sr}(85.9094 \mathrm{amu})\) \(7.00 \%^{87} \operatorname{Sr}(86.9089 \text { amu }),\) and \(82.58 \%^{88} \mathrm{Sr}(87.9056 \mathrm{amu})\) Calculate the average atomic mass of strontium and compare it to the value in the periodic table inside the front COVET.

What are the masses of the formula units of each of the following ionic compounds? (a) \(\mathrm{CaF}_{2} ;\) (b) \(\mathrm{Na}_{2} \mathrm{S} ;\) (c) \(\mathrm{Cr}_{2} \mathrm{O}_{3}\)

What are the masses of the formula units of each of the following ionic compounds? (a) \(\mathrm{KCl} ;\) (b) \(\mathrm{Mg} \mathrm{O} ;\) (c) \(\mathrm{Al}_{2} \mathrm{O}_{3}\)

How many carbon atoms are there in one molecule of each of the following compounds? (a) \(\mathrm{CH}_{4} ;\) (b) \(\mathrm{C}_{3} \mathrm{H}_{8} ;\) (c) \(\mathrm{C}_{6} \mathrm{H}_{6}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\)

Rank the following compounds based on increasing molecular mass. (a) \(\mathrm{CO} ;\) (b) \(\mathrm{Cl}_{2} ;\) (c) \(\mathrm{CO}_{2} ;\) (d) \(\mathrm{NH}_{3} ;\) (e) \(\mathrm{CH}_{4}\)

Rank the following compounds based on decreasing molecular mass. (a) \(\mathrm{H}_{2} ;\) (b) \(\mathrm{Br}_{2} ;\) (c) \(\mathrm{NO}_{2} ;\) (d) \(\mathrm{C}_{2} \mathrm{H}_{2} ;\) (e) \(\mathrm{BF}_{3}\)

In principle, we could use the more familiar unit dozen in place of mole when expressing the quantities of particles (atoms, ions, or molecules). What would be the disadvantage in doing so?

In what way is the molar mass of an ionic compound the same as its formula mass, and in what ways are they different?

Do equal masses of two isotopes of an element contain the same number of atoms?

The natural abundances of the isotopes of an element are given in \(\%\) by mass. Does the same percentage apply to the percent natural abundance by moles?

Earth's atmosphere contains many volatile substances that are present in trace amounts. The following quantities of trace gases were found in a 1.0 mL sample of air. Calculate the number of moles of each gas in the sample. a. \(4.4 \times 10^{14}\) atoms of \(\mathrm{Ne}\) b. \(4.2 \times 10^{13}\) molecules of \(\mathrm{CH}_{4}\) c. \(2.5 \times 10^{12}\) molecules of \(\mathrm{O}_{3}\) d. \(4.9 \times 10^{9}\) molecules of \(\mathrm{NO}_{2}\)

The following quantities of trace gases were found in a 1.0 mL sample of air. Calculate the number of moles of each compound in the sample. a. \(1.4 \times 10^{13}\) molecules of \(\mathrm{H}_{2}\) b. \(1.5 \times 10^{14}\) atoms of \(\mathrm{He}\) c. \(7.7 \times 10^{12}\) molecules of \(\mathrm{N}_{2} \mathrm{O}\) d. \(3.0 \times 10^{12}\) molecules of \(\mathrm{CO}\)

How many moles of iron are there in 1 mole of the following compounds? (a) \(\mathrm{FeO} ;\) (b) \(\mathrm{Fe}_{2} \mathrm{O}_{3} ;\) (c) \(\mathrm{Fe}(\mathrm{OH})_{3}\) (d) \(\mathrm{Fe}_{3} \mathrm{O}_{4}\)

How many moles of \(\mathrm{Na}^{+}\) ions are there in 1 mole of the following compounds? (a) \(\mathrm{NaCl} ;\) (b) \(\mathrm{Na}_{2} \mathrm{SO}_{4} ;\) (c) \(\mathrm{Na}_{3} \mathrm{PO}_{4}\) (d) \(\mathrm{NaNO}_{3}\)

What is the mass of 0.122 mol of \(\mathrm{Mg} \mathrm{CO}_{3} ?\)

What is the volume of 1.00 mol of benzene \(\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)\) at \(20^{\circ} \mathrm{C} ?\) The density of benzene at \(20^{\circ} \mathrm{C}\) is \(0.879 \mathrm{g} / \mathrm{mL}\)

How many moles of titanium and how many atoms of titanium are there in 0.125 mole of each of the following? (a) ilmenite, \(\mathrm{FeTiO}_{3} ;\) (b) \(\mathrm{TiCl}_{4} ;\) (c) \(\mathrm{Ti}_{2} \mathrm{O}_{3} ;\) (d) \(\mathrm{Ti}_{3} \mathrm{O}_{5}\)

How many moles of iron and how many atoms of iron are there in 2.5 moles of each of the following? (a) wolframite, \(\mathrm{FeWO}_{4}\) (b) pyrite, \(\mathrm{FeS}_{2} ;\) (c) magnetite, \(\mathrm{Fe}_{3} \mathrm{O}_{4} ;\) (d) hematite,\(\mathrm{Fe}_{2} \mathrm{O}_{3}\)

Which substance in each of the following pairs of quantities contains more moles of oxygen? a. \(1 \mathrm{mol} \mathrm{Al}_{2} \mathrm{O}_{3}\) or \(1 \mathrm{mol} \mathrm{Fe}_{2} \mathrm{O}_{3}\) b. \(1 \mathrm{mol} \mathrm{SiO}_{2}\) or \(1 \mathrm{mol} \mathrm{N}_{2} \mathrm{O}_{4}\) c. 3 mol \(\mathrm{CO}\) or \(2 \mathrm{mol} \mathrm{CO}_{2}\)