Zinc sulfide (ZnS) occurs in the zinc blende crystal structure. (a) If 2.54 g of ZnS

What is the key difference between an element and a compound?

List two differences between a compound and a mixture.

Which of the following are pure substances? Explain. (a) Calcium chloride, used to melt ice on roads, consists of two elements, calcium and chlorine, in a fixed mass ratio. (b) Sulfur consists of sulfur atoms combined into octatomic molecules. (c) Baking powder, a leavening agent, contains 26% to 30% sodium hydrogen carbonate and 30% to 35% calcium dihydrogen phosphate by mass. (d) Cytosine, a component of DNA, consists of H, C, N, and O atoms bonded in a specific arrangement.

Classify each substance in Problem 2.3 as an element, compound, or mixture, and explain your answers.

Explain the following statement: The smallest particles unique to an element may be atoms or molecules.

Explain the following statement: The smallest particles unique to a compound cannot be atoms.

Can the relative amounts of the components of a mixture vary? Can the relative amounts of the components of a compound vary? Explain.

The tap water found in many areas of the United States leaves white deposits when it evaporates. Is this tap water a mixture or a compound? Explain.

Each scene below represents a mixture. Describe each one in terms of the number(s) of elements and/or compounds present. (a) (b) (c)

Samples of illicit street drugs often contain an inactive component, such as ascorbic acid (vitamin C). After obtaining a sample of cocaine, government chemists calculate the mass of vitamin C per gram of drug sample, and use it to track the drugs distribution. For example, if different samples of cocaine obtained on the streets of New York, Los Angeles, and Paris all contain 0.6384 g of vitamin C per gram of sample, they very likely come from a common source. Do these street samples consist of a compound, element, or mixture? Explain.

Why was it necessary for separation techniques and methods of chemical analysis to be developed before the laws of definite composition and multiple proportions could be formulated?

To which classes of matterelement, compound, and/or mixturedo the following apply: (a) law of mass conservation; (b) law of definite composition; (c) law of multiple proportions?

In our modern view of matter and energy, is the law of mass conservation still relevant to chemical reactions? Explain.

Identify the mass law that each of the following observations demonstrates, and explain your reasoning: (a) A sample of potassium chloride from Chile contains the same percent by mass of potassium as one from Poland. (b) A flashbulb contains magnesium and oxygen before use and magnesium oxide afterward, but its mass does not change. (c) Arsenic and oxygen form one compound that is 65.2 mass % arsenic and another that is 75.8 mass % arsenic.

Which of the following scenes illustrate(s) the fact that compounds of chlorine (green) and oxygen (red) exhibit the law of multiple proportions? Name the compounds. A B C

(a) Does the percent by mass of each element in a compound depend on the amount of compound? Explain. (b) Does the mass of each element in a compound depend on the amount of compound? Explain.

Does the percent by mass of each element in a compound depend on the amount of that element used to make the compound? Explain.

State the mass law(s) demonstrated by the following experimental results, and explain your reasoning: Experiment 1: A student heats 1.00 g of a blue compound and obtains 0.64 g of a white compound and 0.36 g of a colorless gas. Experiment 2: A second student heats 3.25 g of the same blue compound and obtains 2.08 g of a white compound and 1.17 g of a colorless gas.

State the mass law(s) demonstrated by the following experimental results, and explain your reasoning: Experiment 1: A student heats 1.27 g of copper and 3.50 g of iodine to produce 3.81 g of a white compound; 0.96 g of iodine remains. Experiment 2: A second student heats 2.55 g of copper and 3.50 g of iodine to form 5.25 g of a white compound; 0.80 g of copper remains.

Fluorite, a mineral of calcium, is a compound of the metal with fluorine. Analysis shows that a 2.76-g sample of fluorite contains 1.42 g of calcium. Calculate the (a) mass of fluorine in the sample; (b) mass fractions of calcium and fluorine in fluorite; (c) mass percents of calcium and fluorine in fluorite.

Galena, a mineral of lead, is a compound of the metal with sulfur. Analysis shows that a 2.34-g sample of galena contains 2.03 g of lead. Calculate the (a) mass of sulfur in the sample; (b) mass fractions of lead and sulfur in galena; (c) mass percents of lead and sulfur in galena.

Magnesium oxide (MgO) forms when the metal burns in air. (a) If 1.25 g of MgO contains 0.754 g of Mg, what is the mass ratio of magnesium to magnesium oxide? (b) How many grams of Mg are in 534 g of MgO?

Zinc sulfide (ZnS) occurs in the zinc blende crystal structure. (a) If 2.54 g of ZnS contains 1.70 g of Zn, what is the mass ratio of zinc to zinc sulfide? (b) How many kilograms of Zn are in 3.82 kg of ZnS?

A compound of copper and sulfur contains 88.39 g of metal and 44.61 g of nonmetal. How many grams of copper are in 5264 kg of compound? How many grams of sulfur?

A compound of iodine and cesium contains 63.94 g of metal and 61.06 g of nonmetal. How many grams of cesium are in 38.77 g of compound? How many grams of iodine?

Show, with calculations, how the following data illustrate the law of multiple proportions: Compound 1: 47.5 mass % sulfur and 52.5 mass % chlorine Compound 2: 31.1 mass % sulfur and 68.9 mass % chlorine

Show, with calculations, how the following data illustrate the law of multiple proportions: Compound 1: 77.6 mass % xenon and 22.4 mass % fluorine Compound 2: 63.3 mass % xenon and 36.7 mass % fluorine

Dolomite is a carbonate of magnesium and calcium. Analysis shows that 7.81 g of dolomite contains 1.70 g of Ca. Calculate the mass percent of Ca in dolomite. On the basis of the mass percent of Ca, and neglecting all other factors, which is the richer source of Ca, dolomite or fluorite (see Problem 2.20)?

The mass percent of sulfur in a sample of coal is a key factor in the environmental impact of the coal because the sulfur combines with oxygen when the coal is burned and the oxide can then be incorporated into acid rain. Which of the following coals would have the smallest environmental impact? Mass (g) of Mass (g) of Sample Sulfur in Sample Coal A 378 11.3 Coal B 495 19.0 Coal C 675 20.6

Which of Daltons postulates about atoms are inconsistent with later observations? Do these inconsistencies mean that Dalton was wrong? Is Daltons model still useful? Explain.

Use Daltons theory to explain why potassium nitrate from India or Italy has the same mass percents of K, N, and O.

Thomson was able to determine the mass/charge ratio of the electron but not its mass. How did Millikans experiment allow determination of the electrons mass?

The following charges on individual oil droplets were obtained during an experiment similar to Millikans. Determine a charge for the electron (in C, coulombs), and explain your answer: 23.204310219 C; 24.806310219 C; 28.010310219 C; 21.442310218 C.

Describe Thomsons model of the atom. How might it account for the production of cathode rays?

When Rutherfords coworkers bombarded gold foil with a particles, they obtained results that overturned the existing (Thomson) model of the atom. Explain.

Define atomic number and mass number. Which can vary without changing the identity of the element?

Choose the correct answer. The difference between the mass number of an isotope and its atomic number is (a) directly related to the identity of the element; (b) the number of electrons; (c) the number of neutrons; (d) the number of isotopes.

Even though several elements have only one naturally occurring isotope and all atomic nuclei have whole numbers of protons and neutrons, no atomic mass is a whole number. Use the data from Table 2.2 to explain this fact.

Argon has three naturally occurring isotopes, 36Ar, 38Ar, and 40Ar. What is the mass number of each isotope? How many protons, neutrons, and electrons are present in each?

Chlorine has two naturally occurring isotopes, 35Cl and 37Cl. What is the mass number of each isotope? How many protons, neutrons, and electrons are present in each?

Do both members of the following pairs have the same number of protons? Neutrons? Electrons? (a) 16 8O and 17 8O (b) 40 18 Ar and 41 19K (c) 60 27Co and 60Ni 28 Which pair(s) consist(s) of atoms with the same Z value? N value? A value?

Do both members of the following pairs have the same number of protons? Neutrons? Electrons? (a) 3 1H and 3 2He (b) 14 6C and 15 7N (c) 19 9F and 18 9F Which pair(s) consist(s) of atoms with the same Z value? N value? A value?

Write the A ZX notation for each atomic depiction: 18p+ 20n0 18e 25p+ 30n0 25e 47p+ 62n0 47e (a) (b) (c)

Write the A ZX notation for each atomic depiction: 6p+ 7n0 6e 40p+ 50n0 40e 28p+ 33n0

Draw atomic depictions similar to those in Problem 2.43 for (a) 48Ti 22 ; (b) 79 34Se; (c) 11 5B

Draw atomic depictions similar to those in Problem 2.43 for (a) 207 82Pb; (b) 9 4Be; (c) 75As 33 .

Gallium has two naturally occurring isotopes, 69Ga (isotopic mass 5 68.9256 amu, abundance 5 60.11%) and 71Ga (isotopic mass 5 70.9247 amu, abundance 5 39.89%). Calculate the atomic mass of gallium.

Magnesium has three naturally occurring isotopes, 24Mg (isotopic mass 5 23.9850 amu, abundance 5 78.99%), 25Mg (isotopic mass 5 24.9858 amu, abundance 5 10.00%), and 26Mg (isotopic mass 5 25.9826 amu, abundance 5 11.01%). Calculate the atomic mass of magnesium.

Chlorine has two naturally occurring isotopes, 35Cl (isotopic mass 5 34.9689 amu) and 37Cl (isotopic mass 5 36.9659 amu). If chlorine has an atomic mass of 35.4527 amu, what is the percent abundance of each isotope?

Copper has two naturally occurring isotopes, 63Cu (isotopic mass 5 62.9296 amu) and 65Cu (isotopic mass 5 64.9278 amu). If copper has an atomic mass of 63.546 amu, what is the percent abundance of each isotope?

How can iodine (Z 5 53) have a higher atomic number yet a lower atomic mass than tellurium (Z 5 52)?

Correct each of the following statements: (a) In the modern periodic table, the elements are arranged in order of increasing atomic mass. (b) Elements in a period have similar chemical properties. (c) Elements can be classified as either metalloids or nonmetals.

What class of elements lies along the staircase line in the periodic table? How do the properties of these elements compare with those of metals and nonmetals?

What are some characteristic properties of elements to the left of the elements along the staircase? To the right?

The elements in Groups 1A(1) and 7A(17) are all quite reactive. What is a major difference between them?

Give the name, atomic symbol, and group number of the element with each Z value, and classify it as a metal, metalloid, or nonmetal: (a) Z 5 32 (b) Z 5 15 (c) Z 5 2 (d) Z 5 3 (e) Z 5 42

Give the name, atomic symbol, and group number of the element with each Z value, and classify it as a metal, metalloid, or nonmetal: (a) Z 5 33 (b) Z 5 20 (c) Z 5 35 (d) Z 5 19 (e) Z 5 13

Fill in the blanks: (a) The symbol and atomic number of the heaviest alkaline earth metal are ______ and ______. (b) The symbol and atomic number of the lightest metalloid in Group 4A(14) are ______ and ______. (c) Group 1B(11) consists of the coinage metals. The symbol and atomic mass of the coinage metal whose atoms have the fewest electrons are ______ and ______. (d) The symbol and atomic mass of the halogen in Period 4 are ______ and ______.

Fill in the blanks: (a) The symbol and atomic number of the heaviest nonradioactive noble gas are ______ and ______. (b) The symbol and group number of the Period 5 transition element whose atoms have the fewest protons are ______ and ______. (c) The elements in Group 6A(16) are sometimes called the chalcogens. The symbol and atomic number of the first metallic chalcogen are ______ and ______. (d) The symbol and number of protons of the Period 4 alkali metal atom are ______ and ______.

Describe the type and nature of the bonding that occurs between reactive metals and nonmetals.

Describe the type and nature of the bonding that often occurs between two nonmetals.

How can ionic compounds be neutral if they consist of positive and negative ions?

Given that the ions in LiF and in MgO are of similar size, which compound has stronger ionic bonding? Use Coulombs law in your explanation.

Are molecules present in a sample of BaF2? Explain.

Are ions present in a sample of P4O6? Explain.

The monatomic ions of Groups 1A(1) and 7A(17) are all singly charged. In what major way do they differ? Why?

Describe the formation of solid magnesium chloride (MgCl2) from large numbers of magnesium and chlorine atoms.

Describe the formation of solid potassium sulfide (K2S) from large numbers of potassium and sulfur atoms.

Does potassium nitrate (KNO3) incorporate ionic bonding, covalent bonding, or both? Explain.

What monatomic ions would you expect potassium (Z 5 19) and bromine (Z 5 35) to form?

What monatomic ions would you expect radium (Z 5 88) and selenium (Z 5 34) to form?

For each ionic depiction, give the name of the parent atom, its mass number, and its group and period numbers: 8p+ 9n0 10e 9p+ 10n0 10e 20p+ 20n0 18e (a

For each ionic depiction, give the name of the parent atom, its mass number, and its group and period numbers: 35p+ 44n0 36e 10e 37p+ 48n0 36e 7p+ 8n0 (

An ionic compound forms when lithium (Z 5 3) reacts with oxygen (Z 5 8). If a sample of the compound contains 8.431021 lithium ions, how many oxide ions does it contain?

An ionic compound forms when calcium (Z 5 20) reacts with iodine (Z 5 53). If a sample of the compound contains 7.431021 calcium ions, how many iodide ions does it contain?

The radii of the sodium and potassium ions are 102 pm and 138 pm, respectively. Which compound has stronger ionic attractions, sodium chloride or potassium chloride?

The radii of the lithium and magnesium ions are 76 pm and 72 pm, respectively. Which compound has stronger ionic attractions, lithium oxide or magnesium oxide?

What information about the relative numbers of ions and the percent mass of elements is in the formula MgF2?

How is a structural formula similar to a molecular formula? How is it different?

Consider a mixture of 10 billion O2 molecules and 10 billion H2 molecules. In what way is this mixture similar to a sample containing 10 billion hydrogen peroxide (H2O2) molecules? In what way is it different?

For what type(s) of compound do we use Roman numerals in the names?

For what type(s) of compound do we use Greek numerical prefixes in the names?

For what type of compound are we unable to write a molecular formula?

Give the name and formula of the compound formed from the following elements: (a) sodium and nitrogen; (b) oxygen and strontium; (c) aluminum and chlorine.

Give the name and formula of the compound formed from the following elements: (a) cesium and bromine; (b) sulfur and barium; (c) calcium and fluorine.

Give the name and formula of the compound formed from the following elements: (a) 12L and 9M (b) 30L and 16M (c) 17L and 38M

Give the name and formula of the compound formed from the following elements: (a) 37Q and 35R (b) 8Q and 13R (c) 20Q and 53R

Give the systematic names for the formulas or the formulas for the names: (a) tin(IV) chloride; (b) FeBr3; (c) cuprous bromide; (d) Mn2O3.

Give the systematic names for the formulas or the formulas for the names: (a) Na2HPO4; (b) potassium carbonate dihydrate; (c) NaNO2; (d) ammonium perchlorate.

Give the systematic names for the formulas or give the formulas for the names: (a) CoO; (b) mercury(I) chloride; (c) Pb(C2H3O2)2?3H2O; (d) chromic oxide.

Give the systematic names for the formulas or the formulas for the names: (a) Sn(SO3)2; (b) potassium dichromate; (c) FeCO3; (d) copper(II) nitrate.

Correct each of the following formulas: (a) Barium oxide is BaO2 (b) Iron(II) nitrate is Fe(NO3)3 (c) Magnesium sulfide is MnSO3

Correct each of the following names: (a) CuI is cobalt(II) iodide (b) Fe(HSO4)3 is iron(II) sulfate (c) MgCr2O7 is magnesium dichromium heptaoxide

Give the name and formula for the acid derived from each of the following anions: (a) hydrogen carbonate (b) IO4 2 (c) cyanide (d) HS2

Give the name and formula for the acid derived from each of the following anions: (a) perchlorate (b) NO3 2 (c) bromite (d) H2PO4 2

Many chemical names are similar at first glance. Give the formulas of the species in each set: (a) Ammonium ion and ammonia (b) Magnesium sulfide, magnesium sulfite, and magnesium sulfate (c) Hydrochloric acid, chloric acid, and chlorous acid (d) Cuprous bromide and cupric bromide

Give the formulas of the compounds in each set: (a) Lead(II) oxide and lead(IV) oxide (b) Lithium nitride, lithium nitrite, and lithium nitrate (c) Strontium hydride and strontium hydroxide (d) Magnesium oxide and manganese(II) oxide

Give the name and formula of the compound whose molecules consist of two sulfur atoms and four fluorine atoms.

Give the name and formula of the compound whose molecules consist of two chlorine atoms and one oxygen atom.

Correct the name to match the formula of the following compounds: (a) calcium(II) dichloride, CaCl2; (b) copper(II) oxide, Cu2O; (c) stannous tetrafluoride, SnF4; (d) hydrogen chloride acid, HCl.

Correct the formula to match the name of the following compounds: (a) iron(III) oxide, Fe3O4; (b) chloric acid, HCl; (c) mercuric oxide, Hg2O; (d) potassium iodide, P2I3.

Write the formula of each compound, and determine its molecular (formula) mass: (a) ammonium sulfate; (b) sodium dihydrogen phosphate; (c) potassium bicarbonate.

Write the formula of each compound, and determine its molecular (formula) mass: (a) sodium dichromate; (b) ammonium perchlorate; (c) magnesium nitrite trihydrate.

Calculate the molecular (formula) mass of each compound: (a) dinitrogen pentoxide; (b) lead(II) nitrate; (c) calcium peroxide.

Calculate the molecular (formula) mass of each compound: (a) iron(II) acetate tetrahydrate; (b) sulfur tetrachloride; (c) potassium permanganate.

Give the number of atoms of the specified element in a formula unit of each of the following compounds, and calculate the molecular (formula) mass: (a) Oxygen in aluminum sulfate, Al2(SO4)3 (b) Hydrogen in ammonium hydrogen phosphate, (NH4)2HPO4 (c) Oxygen in the mineral azurite, Cu3(OH)2(CO3)2

Give the number of atoms of the specified element in a formula unit of each of the following compounds, and calculate the molecular (formula) mass: (a) Hydrogen in ammonium benzoate, C6H5COONH4 (b) Nitrogen in hydrazinium sulfate, N2H6SO4 (c) Oxygen in the mineral leadhillite, Pb4SO4(CO3)2(OH)2

Give the formula, name, and molecular mass of the following molecules: S O H C (a) (b)

Give the formula, name, and molecular mass of the following molecules: N O H C (a) (b)

Before the use of systematic names, many compounds had common names. Give the systematic name for each of the following: (a) Blue vitriol, CuSO4?5H2O (b) Slaked lime, Ca(OH)2 (c) Oil of vitriol, H2SO4 (d) Washing soda, Na2CO3 (e) Muriatic acid, HCl (f) Epsom salt, MgSO4?7H2O (g) Chalk, CaCO3 (h) Dry ice, CO2 (i) Baking soda, NaHCO3 (j) Lye, NaOH

Each circle contains a representation of a binary compound. Determine its name, formula, and molecular (formula) mass. nitrogen chlorine oxygen (a) (b)

In what main way is separating the components of a mixture different from separating the components of a compound?

What is the difference between a homogeneous and a heterogeneous mixture?

Is a solution a homogeneous or a heterogeneous mixture? Give an example of an aqueous solution.

Classify each of the following as a compound, a homogeneous mixture, or a heterogeneous mixture: (a) distilled water; (b) gasoline; (c) beach sand; (d) wine; (e) air.

Classify each of the following as a compound, a homogeneous mixture, or a heterogeneous mixture: (a) orange juice; (b) vegetable soup; (c) cement; (d) calcium sulfate; (e) tea.

Which separation method is operating in each of the following procedures? (a) Pouring a mixture of cooked pasta and boiling water into a colander (b) Removing colored impurities from raw sugar to make refined sugar

A quality-control laboratory analyzes a product mixture using gas-liquid chromatography. The separation of components is more than adequate, but the process takes too long. Suggest two ways, other than changing the stationary phase, to shorten the analysis time.

Helium is the lightest noble gas and the second most abundant element (after hydrogen) in the universe. (a) The radius of a helium atom is 3.1310211 m; the radius of its nucleus is 2.5310215 m. What fraction of the spherical atomic volume is occupied by the nucleus (V of a sphere 5 4 3pr3)? (b) The mass of a helium-4 atom is 6.64648310224 g, and each of its two electrons has a mass of 9.10939310228 g. What fraction of this atoms mass is contributed by its nucleus?

From the following ions (with their radii in pm), choose the pair that forms the strongest ionic bond and the pair that forms the weakest: Ion: Mg21 K1 Rb1 Ba21 Cl2 O22 I2 Radius: 72 138 152 135 181 140 220

Give the molecular mass of each compound depicted below, and provide a correct name for any that are named incorrectly. monosulfur dichloride Br F S Cl P Cl O N dinitride pentoxide boron fluoride phosphorus trichloride

Polyatomic ions are named by patterns that apply to elements in a given group. Using the periodic table and Table 2.5, give the name of each of the following: (a) SeO4 22; (b) AsO4 32; (c) BrO2 2; (d) HSeO4 2; (e) TeO3 22.

Ammonium dihydrogen phosphate, formed from the reaction of phosphoric acid with ammonia, is used as a crop fertilizer as well as a component of some fire extinguishers. (a) What are the mass percentages of N and P in the compound? (b) How much ammonia is incorporated into 100. g of the compound?

Nitrogen forms more oxides than any other element. The percents by mass of N in three different nitrogen oxides are (I) 46.69%, (II) 36.85%, and (III) 25.94%. For each compound, determine (a) the simplest whole-number ratio of N to O and (b) the number of grams of oxygen per 1.00 g of nitrogen.

The number of atoms in 1 dm3 of aluminum is nearly the same as the number of atoms in 1 dm3 of lead, but the densities of these metals are very different (see Table 1.5). Explain.

You are working in the laboratory preparing sodium chloride. Consider the following results for three preparations of the compound: Case 1: 39.34 g Na 1 60.66 g Cl2 - 100.00 g NaCl Case 2: 39.34 g Na 1 70.00 g Cl2 - 100.00 g NaCl 1 9.34 g Cl2 Case 3: 50.00 g Na 1 50.00 g Cl2 - 82.43 g NaCl 1 17.57 g Na Explain these results in terms of the laws of conservation of mass and definite composition.

Scenes AI depict various types of matter on the atomic scale. Choose the correct scene(s) for each of the following: (a) A mixture that fills its container (b) A substance that cannot be broken down into simpler ones (c) An element with a very high resistance to flow (d) A homogeneous mixture (e) An element that conforms to the walls of its container and displays an upper surface (f) A gas consisting of diatomic particles (g) A gas that can be broken down into simpler substances (h) A substance with a 2/1 ratio of its component atoms (i) Matter that can be separated into its component substances by physical means (j) A heterogeneous mixture (k) Matter that obeys the law of definite composition D E F A B C G H I

The seven most abundant ions in seawater make up more than 99% by mass of the dissolved compounds. Here are their abundances in units of mg ion/kg seawater: chloride 18,980; sodium 10,560; sulfate 2650; magnesium 1270; calcium 400; potassium 380; hydrogen carbonate 140. (a) What is the mass % of each ion in seawater? (b) What percent of the total mass of ions is sodium ion? (c) How does the total mass % of alkaline earth metal ions compare with the total mass % of alkali metal ions? (d) Which make up the larger mass fraction of dissolved components, anions or cations?

The scenes on the next page represent a mixture of two monatomic gases undergoing a reaction when heated. Which mass law(s) is (are) illustrated by this change? 273 K 450 K 650 K

When barium (Ba) reacts with sulfur (S) to form barium sulfide (BaS), each Ba atom reacts with an S atom. If 2.50 cm3 of Ba reacts with 1.75 cm3 of S, are there enough Ba atoms to react with the S atoms (d of Ba 5 3.51 g/cm3; d of S 5 2.07 g/cm3)?

Succinic acid (below) is an important metabolite in biological energy production. Give the molecular formula, molecular mass, and the mass percent of each element in succinic acid. C O H C

Fluoride ion is poisonous in relatively low amounts: 0.2 g of F2 per 70 kg of body weight can cause death. Nevertheless, in order to prevent tooth decay, F2 ions are added to drinking water at a concentration of 1 mg of F2 ion per L of water. How many liters of fluoridated drinking water would a 70-kg person have to consume in one day to reach this toxic level? How many kilograms of sodium fluoride would be needed to treat a 8.503107-gal reservoir?

Antimony has many uses, for example, in infrared devices and as part of an alloy in lead storage batteries. The element has two naturally occurring isotopes, one with mass 120.904 amu, the other with mass 122.904 amu. (a) Write the A ZX notation for each isotope. (b) Use the atomic mass of antimony from the periodic table to calculate the natural abundance of each isotope.

Dinitrogen monoxide (N2O; nitrous oxide) is a greenhouse gas that enters the atmosphere principally from natural fertilizer breakdown. Some studies have shown that the isotope ratios of 15N to 14N and of 18O to 16O in N2O depend on the source, which can thus be determined by measuring the relative abundance of molecular masses in a sample of N2O. (a) What different molecular masses are possible for N2O? (b) The percent abundance of 14N is 99.6%, and that of 16O is 99.8%. Which molecular mass of N2O is least common, and which is most common?

Use the box color(s) in the periodic table below to identify the element(s) described by each of the following: (a) Four elements that are nonmetals (b) Two elements that are metals (c) Three elements that are gases at room temperature (d) Three elements that are solid at room temperature (e) One pair of elements likely to form a covalent compound (f) Another pair of elements likely to form a covalent compound (g) One pair of elements likely to form an ionic compound with formula MX (h) Another pair of elements likely to form an ionic compound with formula MX (i) Two elements likely to form an ionic compound with formula M2X (j) Two elements likely to form an ionic compound with formula MX2 (k) An element that forms no compounds (l) A pair of elements whose compounds exhibit the law of multiple proportions

The two isotopes of potassium with significant abundance in nature are 39K (isotopic mass 38.9637 amu, 93.258%) and 41K (isotopic mass 40.9618 amu, 6.730%). Fluorine has only one naturally occurring isotope, 19F (isotopic mass 18.9984 amu). Calculate the formula mass of potassium fluoride.

Boron trifluoride is used as a catalyst in the synthesis of organic compounds. When this compound is analyzed by mass spectrometry (see Tools of the Laboratory, p. 57), several different 11 ions form, including ions representing the whole molecule as well as molecular fragments formed by the loss of one, two, and three F atoms. Given that boron has two naturally occurring isotopes, 10B and 11B, and fluorine has one, 19F, calculate the masses of all possible 11 ions.

Nitrogen monoxide (NO) is a bioactive molecule in blood. Low NO concentrations cause respiratory distress and the formation of blood clots. Doctors prescribe nitroglycerin, C3H5N3O9, and isoamyl nitrate, (CH3)2CHCH2CH2ONO2, to increase NO. If each compound releases one molecule of NO per atom of N it contains, calculate the mass percent of NO in each.

TNT (trinitrotoluene; below) is used as an explosive in construction. Calculate the mass of each element in 1.00 lb of TNT. O H N C

Nuclei differ in their stability, and some are so unstable that they undergo radioactive decay. The ratio of the number of neutrons to number of protons (N/Z) in a nucleus correlates with its stability. Calculate the N/Z ratio for (a) 144Sm; (b) 56Fe; (c) 20Ne; (d) 107Ag. (e) The radioactive isotope 238U decays in a series of nuclear reactions that includes another uranium isotope, 234U, and three lead isotopes, 214Pb, 210Pb, and 206Pb. How many neutrons, protons, and electrons are in each of these five isotopes?

The anticancer drug Platinol (cisplatin), Pt(NH3)2Cl2, reacts with the cancer cells DNA and interferes with its growth. (a) What is the mass % of platinum (Pt) in Platinol? (b) If Pt costs $51/g, how many grams of Platinol can be made for $1.00 million (assume that the cost of Pt determines the cost of the drug)?

In the periodic table below, give the name, symbol, atomic number, atomic mass, period number, and group number of (a) the building-block elements (red), which occur in nearly every biological molecule, and (b) the macronutrients (green), which are either essential ions in cell fluids or are part of many biomolecules.

The block diagram below classifies the components of matter on the macroscopic scale. Identify blocks (a)(d). Matter Elements (c) (a) (b) Solutions (d)

Which of the steps in the following process involve(s) a physical change and which involve(s) a chemical change? 1 4 5 2 3