What is the difference between an atom and a molecule?

Sulfur \((S)\) and fluorine \((F)\) form several different compounds. One of them, \(\mathrm{SF}_{6}\), contains 3.55 g of \(F\) for every gram of \(S\). Use the law of multiple proportions to determine \(n\), which represents the number of \(F\) atoms in \(\mathrm{SF}_{n}\), given that it contains 2.37 g of \(F\) for every gram of \(S\).

Name of following compounds.

Pair the following species that contain the same number of electrons: \(\text{ Ar,}\mathrm{\ Sn}^{4+},\mathrm{\ F}^-,\mathrm{\ Fe}^{3+},\mathrm{\ P}^{3-},\mathrm{\ V},\mathrm{\ Ag}^+,\mathrm{\ N}^{3-}\)

Write the correct symbols for the atoms that contain: (a) 25 protons, 25 electrons, and 27 neutrons; (b) 10 protons, 10 electrons, and 12 neutrons; (c) 47 protons, 47 electrons, and 60 neutrons; (d) 53 protons, 53 electrons, and 74 neutrons; (e) 94 protons, 94 electrons, and 145 neutrons.

A sample of a uranium compound is found to be losing mass gradually. Explain what is happening to the sample.

In which one of the following pairs do the two species resemble each other most closely in chemical properties? Explain. (a) \({ }_{1}^{1} \mathrm{H}\) and \({ }_{1}^{1} \mathrm{H}^{+}\), (b) \(_7^{14}\mathrm{N}\) and \(_7^{14}\mathrm{N}^{3-}\), (c) \({ }_{6}^{12} \mathrm{C}\) and \({ }_{6}^{13} \mathrm{C}\).

One isotope of a metallic element has mass number 65 and 35 neutrons in the nucleus. The cation derived from the isotope has 28 electrons. Write the symbol for this cation.

One isotope of a nonmetallic element has mass number 127 and 74 neutrons in the nucleus. The anion derived from the isotope has 54 electrons. Write the symbol for this anion.

Determine the molecular and empirical formulas of the compounds shown here. (Black spheres are carbon and gray spheres are hydrogen.)

What is wrong with or ambiguous about the phrase "four molecules of NaCl"?

The following phosphorus sulfides are known: \(\mathrm{P}_4\mathrm{S}_3\), \(\mathrm{P}_4\mathrm{S}_7\), and \(\mathrm{P}_4\mathrm{S}_{10}\). Do these compounds obey the law of multiple proportions?

Which of the following are elements, which are molecules but not compounds, which are compounds but not molecules, and which are both compounds and molecules? (a) \(\mathrm{SO}_{2}\), (b) \(\mathrm{S}_{8}\), (c) \(\mathrm{Cs}\), (d) \(\mathrm{N}_{2} \mathrm{O}_{5}\), (e) \(\mathrm{O}\), (f) \(\mathrm{O}_{2}\), (g) \(\mathrm{O}_{3}\), (h) \(\mathrm{CH}_{4}\), (i) \(\mathrm{KBr}\), (j) \(\mathrm{S}\), (k) \(\mathrm{P}_{4}\), (l) \(\mathrm{LiF}\)

The following table gives numbers of electrons, protons, and neutrons in atoms or ions of a number of elements. Answer the following: (a) Which of the species are neutral? (b) Which are negatively charged? (c) Which are positively charged? (d) What are the conventional symbols for all the species?

Identify the elements represented by the following symbols and give the number of protons and neutrons in each case: (a) \({ }_{10}^{20} \mathrm{X}\), (b) \({ }_{29}^{63} \mathrm{X}\), (c) \({ }_{47}^{107} \mathrm{X}\), (d) \({ }_{74}^{182} \mathrm{X}\), (e) \({ }_{84}^{203} \mathrm{X}\), (f) \({ }_{94}^{234} \mathrm{X}\).

Each of the following pairs of elements will react to form an ionic compound. Write the formulas and name these compounds: (a) barium and oxygen, (b) calcium and phosphorus, (c) aluminum and sulfur, (d) lithium and nitrogen.

Match the descriptions [(a)-(h)] with each of the following elements: \(\mathrm{P},\mathrm{\ Cu},\mathrm{\ Kr},\mathrm{\ Sb},\mathrm{\ Cs},\mathrm{\ Al},\ \mathrm{Sr},\mathrm{\ Cl}\). (a) A transition metal, (b) a nonmetal that forms a -3 ion, (c) a noble gas, (d) an alkali metal, (e) a metal that forms a +3 ion, (f) a metalloid, (g) an element that exists as a diatomic gas molecule, (h) an alkaline earth metal.

Explain why anions are always larger than the atoms from which they are derived, whereas cations are always smaller than the atoms from which they are derived. (Hint: Consider the electrostatic attraction between protons and electrons.)

(a) Describe Rutherford's experiment and how it led to the structure of the atom. How was he able to estimate the number of protons in a nucleus from the scattering of the \(\alpha\) particles? (b) Consider the \({ }^{23} \mathrm{Na}\) atom. Given that the radius and mass of the nucleus are \(3.04\times10^{-15}\mathrm{\ m}\) and \(3.82\times10^{-23}\mathrm{\ g}\), respectively, calculate the density of the nucleus in \(\mathrm{g} / \mathrm{cm}^{3}\). The radius of a \({ }^{23} \mathrm{Na}\) atom is 186 pm. Calculate the density of the space occupied by the electrons in the model of an atom? Do your results support Rutherford’s model of an atom? [The volume of a sphere of radius \(r\) is \((4 / 3) \pi r^{3}\).]

Caffeine, shown here, is a psychoactive stimulant drug. Write the molecular formula and empirical formula of the compound.

Acetaminophen, shown here, is the active ingredient in Tylenol. Write the molecular formula and empirical formula of the compound.

What is wrong with the chemical formula for each of the following compounds: (a) magnesium iodate \(\left[\mathrm{Mg}\left(\mathrm{IO}_{4}\right)_{2}\right]\), (b) phosphoric acid \(\left(\mathrm{H}_{3} \mathrm{PO}_{3}\right)\), (c) barium sulfite \((\mathrm{BaS})\), (d) ammonium bicarbonate \(\left(\mathrm{NH}_{3} \mathrm{HCO}_{3}\right)\)?

What is wrong with the names (in parentheses) for each of the following compounds: \(\mathrm{SnCl}_{4}\) (tin chloride), (b) \(\mathrm{Cu}_{2} \mathrm{O}\) [copper(II) oxide], (c) \(\mathrm{Co}\left(\mathrm{NO}_{3}\right)_{2}\) (cobalt nitrate), (d) \(\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) (sodium chromate)?

Fill in the blanks in the following table.

(a) Which elements are most likely to form ionic compounds? (b) Which metallic elements are most likely to form cations with different charges?

Write the formula of the common ion derived from each of the following: (a) \(\text { Li }\), (b) \(\text { S }\), (c) \(\text { I }\), (d) \(\text { N }\), (e) \(\text { Al }\), (f) \(\text { Cs }\), (g) \(\text { Mg }\)

Which of the following symbols provides more information about the atom: \({ }^{23} \mathrm{Na}\) or \({ }_{11} \mathrm{Na}\)? Explain.

Write the chemical formulas and names of binary acids and oxoacids that contain Group 7A elements. Do the same for elements in Groups 3A, 4A, 5A, and 6A.

Of the 118 elements known, only two are liquids at room temperature \(\left(25^{\circ} \mathrm{C}\right)\). What are they? (Hint: One element is a familiar metal and the other element is in Group 7A.)

For the noble gases (the Group 8A elements), \({ }_{2}^{4} \mathrm{He}\), \({ }_{10}^{20} \mathrm{Ne}\), \({ }_{18}^{40} \mathrm{Ar}\), \({ }_{36}^{84} \mathrm{Kr}\), and \({ }_{54}^{132} \mathrm{Xe}\), (a) determine the number of protons and neutrons in the nucleus of each atom, and (b) determine the ratio of neutrons to protons in the nucleus of each atom. Describe any general trend you discover in the way this ratio changes with increasing atomic number.

List the elements that exist as gases at room temperature. (Hint: Most of these elements can be found in Groups 5A, 6A, 7A, and 8A.)

The Group 1B metals, \(\mathrm{Cu}\), \(\mathrm{Ag}\), and \(\mathrm{Au}\), are called coinage metals. What chemical properties make them specially suitable for making coins and jewelry?

The elements in Group 8A of the periodic table are called noble gases. Can you suggest what "noble" means in this context?

The formula for calcium oxide is \(\mathrm{CaO}\). What are the formulas for magnesium oxide and strontium oxide?

A common mineral of barium is barytes, or barium sulfate \(\left(\mathrm{BaSO}_{4}\right)\). Because elements in the same periodic group have similar chemical properties, we might expect to find some radium sulfate \(\left(\mathrm{RaSO}_{4}\right)\) mixed with barytes since radium is the last member of Group 2A. However, the only source of radium compounds in nature is in uranium minerals. Why?

List five elements each that are (a) named after places, (b) named after people, (c) named after a color. (Hint: See Appendix 1.)

One isotope of a nonmetallic element has mass number 77 and 43 neutrons in the nucleus. The anion derived from the isotope has 36 electrons. Write the symbol for this anion.

Fluorine reacts with hydrogen (H) and deuterium (D) to form hydrogen fluoride (HF) and deuterium fluoride (DF), where deuterium \(\left({ }_{1}^{2} \mathrm{H}\right)\) is an isotope of hydrogen. Would a given amount of fluorine react with different masses of the two hydrogen isotopes? Does this violate the law of definite proportion? Explain.

Predict the formula and name of a binary compound formed from the following elements: (a) \(\mathrm{Na}\) and \(\mathrm{H}\), (b) \(\mathrm{B}\) and \(\mathrm{O}\), (c) \(\mathrm{Na}\) and \(\mathrm{S}\), (d) \(\mathrm{Al}\) and \(\mathrm{F}\), (e) \(\mathrm{F}\) and \(\mathrm{O}\), (f) \(\mathrm{Sr}\) and \(\mathrm{Cl}\).

Identify each of the following elements: (a) a halogen whose anion contains 36 electrons, (b) a radioactive noble gas with 86 protons, (c) a Group 6A element whose anion contains 36 electrons, (d) an alkali metal cation that contains 36 electrons, (e) a Group 4A cation that contains 80 electrons.

Show the locations of (a) alkali metals, (b) alkaline earth metals, (c) the halogens, and (d) the noble gases in the following outline of a periodic table. Also draw dividing lines between metals and metalloids and between metalloids and nonmetals.

Write the molecular formulas for and names of the following compounds.

Fill the blanks in the following table.

Some compounds are better known by their common names than by their systematic chemical names. Give the chemical formulas of the following substances: (a) dry ice, (b) table salt, (c) laughing gas, (d) marble (chalk, limestone), (e) quicklime, (f) slaked lime, (g) baking soda, (h) washing soda, (i) gypsum, (j) milk of magnesia.

On p. 40 it was pointed out that mass and energy are alternate aspects of a single entity called mass-energy. The relationship between these two physical quantities is Einstein's famous equation, \(E=m c^{2}\), where \(E\) is energy, \(m\) is mass, and \(c\) is the speed of light. In a combustion experiment, it was found that 12.096 g of hydrogen molecules combined with 96.000 g of oxygen molecules to form water and released \(1.715\times10^3\mathrm{\ kJ}\) of heat. Calculate the corresponding mass change in this process and comment on whether the law of conservation of mass holds for ordinary chemical processes. (Hint: The Einstein equation can be used to calculate the change in mass as a result of the change in energy. \(1\mathrm{\ J}=1\mathrm{\ kg}\mathrm{\ m}^2/\mathrm{s}^2\) and \(c=3.00\times10^8\mathrm{\ m}/\mathrm{s}\).)

Draw all possible structural formulas of the following hydrocarbons: \(\mathrm{CH}_{4}\), \(\mathrm{C}_{2} \mathrm{H}_{6}\), \(\mathrm{C}_{3} \mathrm{H}_{8}\), \(\mathrm{C}_{4} \mathrm{H}_{10}\), and \(\mathrm{C}_{5} \mathrm{H}_{12}\)

(a) Assuming nuclei are spherical in shape, show that its radius \(r\) is proportional to the cube root of mass number (\(A\)). (b) In general, the radius of a nucleus is given by \(r=r_{0} A^{1 / 3}\), where \(r_{0}\) is a proportionality constant given by \(1.2\times10^{-15}\mathrm{\ m}\). Calculate the volume of the \({ }_{3}^{7} \mathrm{Li}\) nucleus. (c) Given that the radius of a \(\mathrm{Li}\) atom is 152 pm, calculate the fraction of the atom's volume occupied by the nucleus. Does your result support Rutherford's model of an atom?

Draw two different structural formulas based on the molecular formula \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}\). Is the fact that you can have more than one compound with the same molecular formula consistent with Dalton's atomic theory?

Ethane and acetylene are two gaseous hydrocarbons. Chemical analyses show that in one sample of ethane, 2.65 g of carbon are combined with 0.665 g of hydrogen, and in one sample of acetylene, 4.56 g of carbon are combined with 0.383 g of hydrogen. (a) Are these results consistent with the law of multiple proportions? (b) Write reasonable molecular formulas for these compounds.

A cube made of platinum (Pt) has an edge length of 1.0 cm. (a) Calculate the number of Pt atoms in the cube, (b) Atoms are spherical in shape. Therefore, the Pt atoms in the cube cannot fill all of the available space. If only 74 percent of the space inside the cube is taken up by Pt atoms, calculate the radius in picometers of a Pt atom. The density of Pt is 21.45 \(\mathrm{g}/\mathrm{cm}^3\) and the mass of a single Pt atom is \(3.240 \times 10^{-22} \mathrm{g}\). [The volume of a sphere of radius is \((4 / 3) \pi r^{3}\).]

A monatomic ion has a charge of +2. The nucleus of the parent atom has a mass number of 55. If the number of neutrons in the nucleus is 1.2 times that of the number of protons, what is the name and symbol of the element?

In the following \(2 \times 2\) crossword, each letter must be correct four ways: horizontally, vertically, diagonally, and by itself. When the puzzle is complete, the four spaces will contain the overlapping symbols of 10 elements. Use capital letters for each square. There is only one correct solution.* Horizontal 1-2: Two-letter symbol for a metal used in ancient times 3-4: Two-letter symbol for a metal that burns in air and is found in Group 5A Vertical 1-3: Two-letter symbol for a metalloid 2-4: Two-letter symbol for a metal used in U.S. coins Single Squares 1: A colorful nonmetal 2: A colorless gaseous nonmetal 3: An element that makes fireworks green 4: An element that has medicinal uses Diagonal 1-4: Two-letter symbol for an element used in electronics 2-3: Two-letter symbol for a metal used with \(\mathrm{Zr}\) to make wires for superconducting magnets

Why do all atoms of an element have the same atomic number, although they may have different mass numbers?

What do we call atoms of the same elements with different mass numbers?

Explain the meaning of each term in the symbol \({ }_{Z}^{A} \mathrm{X}\).

What is the mass number of an iron atom that has 28 neutrons?

Calculate the number of neutrons of \({ }^{239} \mathrm{Pu}\).

For each of the following species, determine the number of protons and the number of neutrons in the nucleus: \(_2^3\mathrm{He},\ _2^4\mathrm{He},\ _{12}^{24}\mathrm{Mg},\ _{12}^{25}\mathrm{Mg},\ _{22}^{48}\mathrm{Ti},\ _{35}^{79}\mathrm{Br},\ _{78}^{195}\mathrm{Pt}\)

Indicate the number of protons, neutrons, and electrons in each of the following species: \(_7^{15}\mathrm{N},\ _{16}^{33}\mathrm{S},\ _{29}^{63}\mathrm{Cu},\ _{38}^{84}\mathrm{Sr},\ _{56}^{130}\mathrm{Ba},\ _{74}^{186}\mathrm{W},\ _{80}^{202}\mathrm{Hg}\)

Write the appropriate symbol for each of the following isotopes: (a) Z = 11, A = 23; (b) Z = 28, A = 64.

Write the appropriate symbol for each of the following isotopes: (a) Z = 74, A = 186; (b) Z = 80, A = 201.

What is the periodic table, and what is its significance in the study of chemistry?

State two differences between a metal and a nonmetal.

Write the names and symbols for four elements in each of the following categories: (a) nonmetal, (b) metal, (c) metalloid.

Define, with two examples, the following terms: (a) alkali metals, (b) alkaline earth metals, (c) halogens, (d) noble gases.

Elements whose names end with \(-ium\) are usually metals; sodium is one example. Identify a nonmetal whose name also ends with \(-ium\).

Describe the changes in properties (from metals to nonmetals or from nonmetals to metals) as we move (a) down a periodic group and (b) across the periodic table from left to right.

Consult a handbook of chemical and physical data (ask your instructor where you can locate a copy of the handbook) to find (a) two metals less dense than water, (b) two metals more dense than mercury, (c) the densest known solid metallic element, (d) the densest known solid nonmetallic element.

Group the following elements in pairs that you would expect to show similar chemical properties: \(K, \ F, \ P, \ Na, \ Cl,\) and \(N\).

What are allotropes? Give an example. How are allotropes different from isotopes?

What is the difference between an atom and a molecule?

Describe the two commonly used molecular models.

Give an example of each of the following: (a) a monatomic cation, (b) a monatomic anion, (c) a polyatomic cation, (d) a polyatomic anion.

Which of the following diagrams represent diatomic molecules, polyatomic molecules, molecules that are not compounds, molecules that are compounds, or an elemental form of the substance?

Which of the following diagrams represent diatomic molecules, polyatomic molecules, molecules that are not compounds, molecules that are compounds, or an elemental form of the substance?

Identify the following as elements or compounds: \(\mathrm{NH}_3,\mathrm{\ N}_2,\mathrm{\ S}_8,\mathrm{\ NO},\mathrm{\ CO},\mathrm{\ CO}_2,\mathrm{\ H}_2,\mathrm{\ SO}_2\)

Give two examples of each of the following: (a) a diatomic molecule containing atoms of the same element, (b) a diatomic molecule containing atoms of different elements, (c) a polyatomic molecule containing atoms of the same element, (d) a polyatomic molecule containing atoms of different elements.

Give the number of protons and electrons in each of the following common ions: \(\mathrm{Na}^+,\mathrm{\ Ca}^{2+},\mathrm{\ Al}^{3+},\mathrm{\ Fe}^{2+},\ \mathrm{I}^-,\mathrm{\ F}^-,\mathrm{\ S}^{2-},\mathrm{\ O}^{2-}\) and \(\mathrm{N}^{3-}\).

Give the number of protons and electrons in each of the following common ions: \(\mathrm{K}^+,\mathrm{\ Mg}^{2+},\mathrm{\ Fe}^{3+},\mathrm{\ Br}^-,\mathrm{\ Mn}^{2+},\mathrm{\ C}^{4-},\ \mathrm{Cu}^{2+}\)

What does a chemical formula represent? What is the ratio of the atoms in the following molecular formulas? (a) NO, (b) \(\mathrm{NCl}_{3}\), (c) \(\mathrm{N}_{2} \mathrm{O}_{4}\), (d) \(\mathrm{P}_{4} \mathrm{O}_{6}\)

Define molecular formula and empirical formula. What are the similarities and differences between the empirical formula and molecular formula of a compound?

Give an example of a case in which two molecules have different molecular formulas but the same empirical formula.

What does \(P_4\) signify? How does it differ from 4P?

What is an ionic compound? How is electrical neutrality maintained in an ionic compound?

Explain why the chemical formulas of ionic compounds are usually the same as their empirical formulas.

Write the formulas for the following ionic compounds: (a) sodium oxide, (b) iron sulfide (containing the \(\mathrm{Fe}^{2+}\) ion), (c) cobalt sulfate containing the \(\mathrm{Co}^{3+}\) and \(\mathrm{SO}_{4}^{2-}\) ions), and (d) barium fluoride. (Hint: See Figure 2.11.)

Write the formulas for the following ionic compounds: (a) copper bromide (containing the \(Cu^+\) ion), (b) manganese oxide (containing the \(Mn^{3+}\) ion), (c) mercury iodide (containing the \({Hg}_2^{2+}\) ion), and (d) magnesium phosphate (containing the \({PO}_{4}^{3-}\) ion).(Hint: See Figure 2.11.)

What are the empirical formulas of the following compounds? (a) \(\mathrm{C}_2\mathrm{N}_2\), (b) \(\mathrm{C}_{6} \mathrm{H}_{6}\), (c) \(\mathrm{C}_{9} \mathrm{H}_{20}\), (d) \(\mathrm{P}_{4} \mathrm{O}_{10}\), (e) \(\mathrm{B}_{2} \mathrm{H}_{6}\)

What are the empirical formulas of the following compounds? (a) \(\mathrm{Al}_{2} \mathrm{Br}_{6}\), (b) \(\mathrm{Na}_2\mathrm{S}_2\mathrm{O}_4\), (c) \(\mathrm{N}_{2} \mathrm{O}_{5}\), (d) \(\mathrm{K}_2\mathrm{Cr}_2\mathrm{O}_7\)

Write the molecular formula of glycine, an amino acid present in proteins. The color codes are: black (carbon), blue (nitrogen), red (oxygen), and gray (hydrogen).

Write the molecular formula of ethanol. The color codes are: black (carbon), red (oxygen), and gray (hydrogen).

Which of the following compounds are likely to be ionic? Which are likely to be molecular? \(\mathrm{SiCl}_4,\mathrm{\ LiF},\ \mathrm{BaCl}_2,\mathrm{\ B}_2\mathrm{H}_6,\mathrm{\ KCl},\mathrm{\ C}_2\mathrm{H}_4\)

Which of the following compounds are likely to be ionic? Which are likely to be molecular? \(\mathrm{CH}_4,\mathrm{\ NaBr},\ \mathrm{BaF}_2,\mathrm{\ CCl}_4,\mathrm{\ ICl},\mathrm{\ CsCl},\mathrm{\ NF}_3\)

What is the difference between inorganic compounds and organic compounds?

What are the four major categories of inorganic compounds?

Give an example each for a binary compound and a ternary compound.

What is the Stock system? What are its advantages over the older system of naming cations?

Explain why the formula HCl can represent two different chemical systems.

Define the following terms: acids, bases, oxoacids, oxoanions, and hydrates.

Name these compounds: (a) \(\mathrm{Na}_{2} \mathrm{CrO}_{4}\), (b) \(\mathrm{K}_{2} \mathrm{HPO}_{4}\), (c) \(\mathrm{HBr}\) (gas), (d) \(\mathrm{HBr}\) (in water), (e) \(\mathrm{Li}_{2} \mathrm{CO}_{3}\), (f) \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\), (g) \(\mathrm{NH}_{4} \mathrm{NO}_{2}\), (h) \(\mathrm{PF}_{3}\), (i) \(\mathrm{PF}_{5}\), (j) \(\mathrm{P}_{4} \mathrm{O}_{6}\), (k) \(\mathrm{CdI}_{2}\), (l) \(\mathrm{SrSO}_{4}\), (m) \(\mathrm{Al}(\mathrm{OH})_{3}\), (n) \(\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O}\).

Name these compounds: (a) KCIO, (b) \(\mathrm{Ag}_{2} \mathrm{CO}_{3}\), (c) \(\mathrm{FeCl}_{2}\), (d) \(\mathrm{KMnO}_{4}\), (e) \(\mathrm{CsClO}_{3}\), (f) HIO, (g) FeO, (h) \(\mathrm{Fe}_{2} \mathrm{O}_{3}\), (i) \(\mathrm{TiCl}_{4}\), (j) NaH, (k) \(\mathrm{Li}_3\mathrm{N}\), (l) \(\mathrm{Na}_{2} \mathrm{O}\), (m) \(\mathrm{Na}_{2} \mathrm{O}_{2}\), (n) \(\mathrm{FeCl}_{3} \cdot 6 \mathrm{H}_{2} \mathrm{O}\).

Write the molecular formula of chloroform, which is used as a solvent and a cleansing agent. The ball-and-stick model of chloroform is shown in the margin on p. 54.

In viewing the periodic table, do chemical properties change more markedly across a period or down a group?

(a) What does \(\mathrm{S}_{8}\) signify? How does it differ from 8S? (b) Determine the number of protons and electrons for the following ions: (a) \(\mathrm{P}^{3-}\) and (b) \(\mathrm{Ti}^{4+}\).

Define the following terms: (a) \(\alpha\) particle, (b) \(\beta\) particle, (c) \(\gamma\) ray, (d) X ray.

How many protons, neutrons, and electrons are in the following isotope of copper: \({ }^{63} \mathrm{Cu}\)?

The atoms of elements \(A\) (blue) and \(B\) (orange) form two compounds shown here. Do these compounds obey the law of multiple proportions?

Name the types of radiation known to be emitted by radioactive elements.

(a) What is the atomic number of an element if one of its isotopes has 117 neutrons and a mass number of 195? (b) Which of the following two symbols provides more information? \({ }^{17} \mathrm{O}\) or \({ }_{8} \mathrm{O}\).

Compare the properties of the following: \(\alpha\) particles, cathode rays, protons, neutrons, electrons.

Write the empirical formula for nicotine \(\left(\mathrm{C}_{10}\mathrm{H}_{14}\mathrm{N}_2\right)\), an addictive drug present in tobacco.

What is meant by the term "fundamental particle"?

Write the formulas of the following ionic compounds: (a) chromium sulfate (containing the \(\mathrm{Cr}^{3+}\) and \(\mathrm{SO}_{4}^{2-}\) ions) and (b) titanium oxide (containing the \(\mathrm{Ti}^{4+}\) and \(\mathrm{O}^{2-}\) ions).

Describe the contributions of the following scientists to our knowledge of atomic structure: J. J. Thomson, R. A. Millikan, Ernest Rutherford, James Chadwick.

Name the following compounds: (a) \(\mathrm{V}_{2} \mathrm{O}_{5}\), and (b) \(\mathrm{Li}_{2} \mathrm{SO}_{3}\).

Match each of the diagrams shown here with the following ionic compounds: \(\mathrm{Al}_{2} \mathrm{O}_{3}\), \(LiH\), \(\mathrm{Na}_2\mathrm{S}\), \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\). (Green spheres represent cations and red spheres represent anions.)

Describe the experimental basis for believing that the nucleus occupies a very small fraction of the volume of the atom.

Write formulas for the following ionic compounds: (a) rubidium sulfate and (b) barium hydride.

The diameter of a helium atom is about \(1\times10^2\mathrm{\ pm}\). Suppose that we could line up helium atoms side by side in contact with one another. Approximately how many atoms would it take to make the distance from end to end 1 cm?

Name the following molecular compounds: (a) \(\mathrm{NF}_{3}\) and (b) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\).

Roughly speaking, the radius of an atom is about 10,000 times greater than that of its nucleus. If an atom were magnified so that the radius of its nucleus became 2.0 cm, about the size of a marble, what would be the radius of the atom in miles? (1 mi = 1609 m.)

Write chemical formulas for the following molecular compounds: (a) sulfur tetrafluoride and (b) dinitrogen pentoxide.

Use the helium-4 isotope to define atomic number and mass number. Why does a knowledge of atomic number enable us to deduce the number of electrons present in an atom?

Name the following oxoacid and oxoanion: (a) \(\mathrm{HBrO}\) and (b) \(\mathrm{HSO}_{4}^{-}\).

Write the formulas for the following compounds: (a) rubidium nitrite, (b) potassium sulfide, (c) sodium hydrogen sulfide, (d) magnesium phosphate, (e) calcium hydrogen phosphate, (f) potassium dihydrogen phosphate, (g) iodine heptafluoride, (h) ammonium sulfate, (i) silver perchlorate, (j) boron trichloride.

Write the formulas for the following compounds: (a) copper(I) cyanide, (b) strontium chlorite, (c) perbromic acid, (d) hydroiodic acid, (e) disodium ammonium phosphate, (f) lead(II) carbonate, (g) tin(II) fluoride, (h) tetraphosphorus decasulfide, (i) mercury(II) oxide, (j) mercury(I) iodide, (k) selenium hexafluoride.

Name the following acids.

Calculate the density of the nucleus of a \({ }_{26}^{56} \mathrm{Fe}\) atom, given that the nuclear mass is \(9.229\times10^{-23}\mathrm{\ g}\). From your result, comment on the fact that any nucleus containing more than one proton must have neutrons present as well. (Hint: See Problem 2.106.)

Element \(\mathrm{X}\) reacts with element \(\mathrm{Y}\) to form an ionic compound containing \(\mathrm{X}^{4+}\) and \(\mathrm{Y}^{2-}\) ions. Write a formula for the compound and suggest in which periodic groups these elements are likely to be found. Name a representative compound.

Methane, ethane, and propane are shown in Table 2.8. Show that the following data are consistent with the law of multiple proportions.

In the Rutherford scattering experiment, an \(\alpha\) particle is heading directly toward a gold nucleus. The particle will come to a halt when its kinetic energy is completely converted to electrical potential energy. When this happens, how close will the \(\alpha\) particle with a kinetic energy of \(6.0\times10^{-14}\mathrm{\ J}\) be from the nucleus? [According to Coulomb's law, the electrical potential energy between two charged particles is \(E=k Q_{1} Q_{2} / r\), where \(Q_{1}\) and \(Q_{2}\) are the charges in coulombs) of the \(\alpha\) particle and the gold nucleus, \(r\) is the distance of separation in meters, and \(k\) is a constant equal to \(9.0\times10^9\mathrm{\ kg}\cdot\mathrm{m}^3/\mathrm{s}^2\cdot\mathrm{C}^2\). Joule (\(\mathrm{J}\)) is the unit of energy where \(1\mathrm{\ J}=1\mathrm{\ kg}\cdot\mathrm{m}^2/\mathrm{s}^2\).]

Estimate the relative sizes of the following species: \(\mathrm{Li},\mathrm{\ Li}^+,\mathrm{\ Li}^-\).

Compare the atomic size of the following two magnesium isotopes: \({ }^{24} \mathrm{Mg}\) and \({ }^{26} \mathrm{Mg}\).

Using visible light, we humans cannot see any object smaller than \(2\times10^{-5}\mathrm{\ cm}\) with an unaided eye. Roughly how many silver atoms must be lined up for us to see the atoms?

If the size of the nucleus of an atom were that of a pea, how far would the electrons be (on average) from the nucleus in meters?

Sodium and potassium are roughly equal in natural abundance in Earth's crust and most of their compounds are soluble. However, the composition of seawater is much higher in sodium than potassium. Explain.

One technique proposed for recycling plastic grocery bags is to heat them at \(700^{\circ} \mathrm{C}\) and high pressure to form carbon microspheres that can be used in a number of applications. Electron microscopy shows some representative carbon microspheres obtained in this manner, where the scale is given in the bottom right corner of the figure. Determine the number of carbon atoms in a typical carbon microsphere.

How many different molecules can you generate by replacing one \(\mathrm{H}\) atom with a hydroxyl group \((-\mathrm{OH})\) in butane (see Table 2.8)?