Chapter 2

Selenium, an element required nutritionally in trace quantities, forms compounds analogous to sulfur. Name the following ions: (a) \(\mathrm{SeO}_{4}{\underline{\phantom{xx}}}^{2-}\), (b) \(\mathrm{Se}^{2-}\), (c) \(\mathrm{HSe}^{-}\), (d) \(\mathrm{HSeO}_{3}^{-}\).

Give the names and charges of the cation and anion in each of the following compounds: (a) \(\mathrm{CaO}\), (b) \(\mathrm{Na}_{2} \mathrm{SO}_{4}\), (c) \(\mathrm{KClO}_{4}\), (d) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\), (e) \(\mathrm{Cr}(\mathrm{OH})_{3}\).

Give the names and charges of the cation and anion in each of the following compounds: (a) \(\mathrm{CuS}\), (b) \(\mathrm{Ag}_{2} \mathrm{SO}_{4}\), (c) \(\mathrm{Al}\left(\mathrm{ClO}_{3}\right)_{3}\), (d) \(\mathrm{Co}(\mathrm{OH})_{2}\), (e) \(\mathrm{PbCO}_{3}\).

Name the following ionic compounds: (a) \(\mathrm{Li}_{2} \mathrm{O}\), (b) \(\mathrm{FeCl}_{3}\), (c) \(\mathrm{NaClO}\), (d) \(\mathrm{CaSO}_{3}\), (e) \(\mathrm{Cu}(\mathrm{OH})_{2}\), (f) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\), (g) \(\mathrm{Ca}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2}\), (h) \(\mathrm{Cr}_{2}\left(\mathrm{CO}_{3}\right)_{3}\), (i) \(\mathrm{K}_{2} \mathrm{CrO}_{4},(\mathbf{j})\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\).

Name the following ionic compounds: (a) \(\mathrm{KCN}\), (b) \(\mathrm{NaBrO}_{2}\), (c) \(\mathrm{Sr}(\mathrm{OH})_{2}\), (d) \(\mathrm{CoTe}\), (e) \(\mathrm{Fe}_{2}\left(\mathrm{CO}_{3}\right)_{3}\), (f) \(\mathrm{Cr}\left(\mathrm{NO}_{3}\right)_{3}\), (g) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{3}\), (h) \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\), (i) \(\mathrm{KMnO}_{4}\), (j) \(\mathrm{Ag}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\).

Write the chemical formulas for the following compounds: (a) aluminum hydroxide, (b) potassium sulfate, (c) copper(I) oxide, (d) zinc nitrate, (e) mercury(II) bromide, (f) iron(III) carbonate, (g) sodium hypobromite.

Give the chemical formula for each of the following ionic compounds: (a) sodium phosphate, (b) zinc nitrate, (c) barium bromate, (d) iron(II) perchlorate, (e) cobalt(II) hydrogen carbonate, (f) chromium(III) acetate, (g) potassium dichromate.

Give the name or chemical formula, as appropriate, for each of the following acids: (a) \(\mathrm{HBrO}_{3}\), (b) \(\mathrm{HBr}\), (c) \(\mathrm{H}_{3} \mathrm{PO}_{4}\), (d) hypochlorous acid, (e) iodic acid, (f) sulfurous acid.

Provide the name or chemical formula, as appropriate, for each of the following acids: (a) hydroiodic acid, (b) chloric acid, (c) nitrous acid, (d) \(\mathrm{H}_{2} \mathrm{CO}_{3}\), (e) \(\mathrm{HClO}_{4}\), (f) \(\mathrm{CH}_{3} \mathrm{COOH}\).

Give the name or chemical formula, as appropriate, for each of the following binary molecular substances: (a) \(\mathrm{SF}_{6}\), (b) \(\mathrm{IF}_{5}\), (c) \(\mathrm{XeO}_{3}\), (d) dinitrogen tetroxide, (e) hydrogen cyanide, (f) tetraphosphorus hexasulfide.

The oxides of nitrogen are very important components in urban air pollution. Name each of the following compounds: (a) \(\mathrm{N}_{2} \mathrm{O}\), (b) \(\mathrm{NO}\), (c) \(\mathrm{NO}_{2}\), (d) \(\mathrm{N}_{2} \mathrm{O}_{5}\), (e) \(\mathrm{N}_{2} \mathrm{O}_{4}\).

Write the chemical formula for each substance mentioned in the following word descriptions (use the front inside cover to find the symbols for the elements you do not know). (a) Zinc carbonate can be heated to form zinc oxide and carbon dioxide. (b) On treatment with hydrofluoric acid, silicon dioxide forms silicon tetrafluoride and water. (c) Sulfur dioxide reacts with water to form sulfurous acid. (d) The substance phosphorus trihydride, commonly called phosphine, is a toxic gas. (e) Perchloric acid reacts with cadmium to form cadmium(II) perchlorate. (f) Vanadium(III) bromide is a colored solid.

Assume that you encounter the following sentences in your reading. What is the chemical formula for each substance mentioned? (a) Sodium hydrogen carbonate is used as a deodorant. (b) Calcium hypochlorite is used in some bleaching solutions. (c) Hydrogen cyanide is a very poisonous gas. (d) Magnesium hydroxide is used as a cathartic. (e) Tin(II) fluoride has been used as a fluoride additive in toothpastes. (f) When cadmium sulfide is treated with sulfuric acid, fumes of hydrogen sulfide are given off.

(a) What is a hydrocarbon? (b) Pentane is the alkane with a chain of five carbon atoms. Write a structural formula for this compound and determine its molecular and empirical formulas.

(a) What is meant by the term isomer? (b) Among the four alkanes, ethane, propane, butane, and pentane, which is capable of existing in isomeric forms?

(a) What is a functional group? (b) What functional group characterizes an alcohol? (c) Write a structural formula for 1-pentanol, the alcohol derived from pentane by making a substitution on one of the carbon atoms.

(a) What do ethane and ethanol have in common? (b) How does 1-propanol differ from propane?

Chloropropane is derived from propane by substituting \(\mathrm{Cl}\) for H on one of the carbon atoms. (a) Draw the structural formulas for the two isomers of chloropropane. (b) Suggest names for these two compounds.

Draw the structural formulas for three isomers of pentane, \(\mathrm{C}_{5} \mathrm{H}_{12}\).

Suppose a scientist repeats the Millikan oil-drop experiment but reports the charges on the drops using an unusual (and imaginary) unit called the warmomb (wa). The scientist obtains the following data for four of the drops: $$ \begin{array}{c|c} \hline \text { Droplet } & \text { Calculated Charge (wa) } \\ \hline \text { A } & 3.84 \times 10^{-8} \\ \text { B } & 4.80 \times 10^{-8} \\ \text { C } & 2.88 \times 10^{-8} \\ \text { D } & 8.64 \times 10^{-8} \\ \hline \end{array} $$ (a) If all the droplets were the same size, which would fall most slowly through the apparatus? (b) From these data, what is the best choice for the charge of the electron in warmombs? (c) Based on your answer to part (b), how many electrons are there on each of the droplets? (d) What is the conversion factor between warmombs and coulombs?

The natural abundance of \({ }^{3} \mathrm{He}\) is \(0.000137 \%\). (a) How many protons, neutrons, and electrons are in an atom of \({ }^{3} \mathrm{He}\) ? (b) Based on the sum of the masses of their subatomic particles, which is expected to be more massive, an atom of \({ }^{3} \mathrm{He}\) or an atom of \({ }^{3} \mathrm{H}\) (which is also called tritium)? (c) Based on your answer to part (b), what would need to be the precision of a mass spectrometer that is able to differentiate between peaks that are due to \({ }^{3} \mathrm{He}^{+}\)and \({ }^{3} \mathrm{H}^{+}\)?

A cube of gold that is \(1.00 \mathrm{~cm}\) on a side has a mass of \(19.3 \mathrm{~g}\). A single gold atom has a mass of \(197.0\) amu. (a) How many gold atoms are in the cube? (b) From the information given, estimate the diameter in ? of a single gold atom. (c) What assumptions did you make in arriving at your answer for part (b)?

The diameter of a rubidium atom is \(4.95 \AA\). We will consider two different ways of placing the atoms on a surface. In arrangement A, all the atoms are lined up with one another to form a square grid. Arrangement B is called a close-packed arrangement because the atoms sit in the "depressions" formed by the previous row of atoms: (a) Using arrangement \(A\), how many Rb atoms could be placed on a square surface that is \(1.0 \mathrm{~cm}\) on a side? (b) How many Rb atoms could be placed on a square surface that is \(1.0 \mathrm{~cm}\) on a side, using arrangement B? (c) By what factor has the number of atoms on the surface increased in going to arrangement \(B\) from arrangement A? If extended to three dimensions, which arrangement would lead to a greater density for Rb metal?

(a) Assuming the dimensions of the nucleus and atom shown in Figure 2.11, what fraction of the volume of the atom is taken up by the nucleus? (b) Using the mass of the proton from Table \(2.1\) and assuming its diameter is \(1.0 \times 10^{-15} \mathrm{~m}\), calculate the density of a proton in \(\mathrm{g} / \mathrm{cm}^{3}\).

Identify the element represented by each of the following symbols and give the number of protons and neutrons in each: (a) \({ }_{33}^{74} \mathrm{X}\), (b) \({ }_{53}^{127} \mathrm{X}\), (c) \({ }_{63}^{152} \mathrm{X}\), (d) \({ }_{83}^{209} \mathrm{X}\).

The nucleus of \({ }^{6} \mathrm{Li}\) is a powerful absorber of neutrons. It exists in the naturally occurring metal to the extent of \(7.5 \%\). In the era of nuclear deterrence, large quantities of lithium were processed to remove \({ }^{6} \mathrm{Li}\) for use in hydrogen bomb production. The lithium metal remaining after removal of \({ }^{6} \mathrm{Li}\) was sold on the market. (a) What are the compositions of the nuclei of \({ }^{6} \mathrm{Li}\) and \({ }^{7} \mathrm{Li}\) ? (b) The atomic masses of \({ }^{6} \mathrm{Li}\) and \({ }^{7} \mathrm{Li}\) are \(6.015122\) and 7.016004 amu, respectively. A sample of lithium depleted in the lighter isotope was found on analysis to contain \(1.442 \%^{6} \mathrm{Li}\). What is the average atomic weight of this sample of the metal?

The element oxygen has three naturally occurring isotopes, with 8,9 , and 10 neutrons in the nucleus, respectively. (a) Write the full chemical symbols for these three isotopes. (b) Describe the similarities and differences between the three kinds of atoms of oxygen.

The element lead ( \(\mathrm{Pb}\) ) consists of four naturally occurring isotopes with atomic masses \(203.97302,205.97444,206.97587\), and \(207.97663\) amu. The relative abundances of these four isotopes are \(1.4,24.1,22.1\), and \(52.4 \%\) respectively. From these data, calculate the atomic weight of lead.

Gallium (Ga) consists of two naturally occurring isotopes with masses of \(68.926\) and \(70.925\) amu. (a) How many protons and neutrons are in the nucleus of each isotope? Write the complete atomic symbol for each, showing the atomic number and mass number. (b) The average atomic mass of Ga is \(69.72\) amu. Calculate the abundance of each isotope.

Using a suitable reference such as the CRC Handbook of Chemistry and Physics or http://www.webelements.com, look up the following information for nickel: (a) the number of known isotopes, (b) the atomic masses (in amu), (c) the natural abundances of the five most abundant isotopes.

There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of \(\mathrm{Br}_{2}\) molecules, and the mass of a Br molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of \(\mathrm{Br}_{2}\) consists of three peaks: (a) What is the origin of each peak (of what isotopes does each consist)? (b) What is the mass of each isotope? (c) Determine the average molecular mass of a \(\mathrm{Br}_{2}\) molecule. (d) Determine the average atomic mass of a bromine atom. (e) Calculate the abundances of the two isotopes.

From the following list of elements-Ar, H, Ga, Al, Ca, Br, \(\mathrm{Ge}, \mathrm{K}, \mathrm{O}\) - pick the one that best fits each description. Use each element only once: (a) an alkali metal, (b) an alkaline earth metal, (c) a noble gas, (d) a halogen, (e) a metalloid, (f) a nonmetal listed in group \(1 \mathrm{~A},(\mathrm{~g})\) a metal that forms a \(3+\) ion, (h) a nonmetal that forms a \(2-\) ion, (i) an element that resembles aluminum.

The first atoms of seaborgium (Sg) were identified in 1974 . The longest-lived isotope of Sg has a mass number of 266 . (a) How many protons, electrons, and neutrons are in an \({ }^{266} \mathrm{Sg}\) atom? (b) Atoms of \(\mathrm{Sg}\) are very unstable, and it is therefore difficult to study this element's properties. Based on the position of \(\mathrm{Sg}\) in the periodic table, what element should it most closely resemble in its chemical properties?

The explosion of an atomic bomb releases many radioactive isotopes, including strontium- 90 . Considering the location of strontium in the periodic table, suggest a reason for the fact that this isotope is particularly dangerous for human health.

Name each of the following oxides. Assuming that the compounds are ionic, what charge is associated with the metallic element in each case? (a) \(\mathrm{NiO}\), (b) \(\mathrm{MnO}_{2}\), (c) \(\mathrm{Cr}_{2} \mathrm{O}_{3}\), (d) \(\mathrm{MoO}_{3}\).

Elements in the same group of the periodic table often form oxyanions with the same general formula. The anions are also named in a similar fashion. Based on these observations, suggest a chemical formula or name, as appropriate, for each of the following ions: (a) \(\mathrm{BrO}_{4}^{-}\), (b) \(\mathrm{SeO}_{3}{\underline{\phantom{xx}}}^{2-}\), (c) arsenate ion, (d) hydrogen tellurate ion.

Carbonic acid occurs in carbonated beverages. When allowed to react with lithium hydroxide, it produces lithium carbonate. Lithium carbonate is used to treat depression and bipolar disorder. Write chemical formulas for carbonic acid, lithium hydroxide, and lithium carbonate.

Give the chemical names of each of the following familiar compounds: (a) \(\mathrm{NaCl}\) (table salt), (b) \(\mathrm{NaHCO}_{3}\) (baking soda), (c) \(\mathrm{NaOCl}\) (in many bleaches), (d) \(\mathrm{NaOH}\) (caustic soda), (e) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}\) (smelling salts), (f) \(\mathrm{CaSO}_{4}\) (plaster of Paris).

Many familiar substances have common, unsystematic names. For each of the following, give the correct systematic name: (a) saltpeter, \(\mathrm{KNO}_{3}\); (b) soda ash, \(\mathrm{Na}_{2} \mathrm{CO}_{3} ;\) (c) lime, \(\mathrm{CaO}\); (d) muriatic acid, \(\mathrm{HCl}\); (e) Epsom salts, \(\mathrm{MgSO}_{4}\); (f) milk of magnesia, \(\mathrm{Mg}(\mathrm{OH})_{2}\).

Because many ions and compounds have very similar names, there is great potential for confusing them. Write the correct chemical formulas to distinguish between (a) calcium sulfide and calcium hydrogen sulfide, (b) hydrobromic acid and bromic acid, (c) aluminum nitride and aluminum nitrite, (d) iron(II) oxide and iron(III) oxide, (e) ammonia and ammonium ion, (f) potassium sulfite and potassium bisulfite, (g) mercurous chloride and mercuric chloride, (h) chloric acid and perchloric acid.

In what part of the atom does the strong nuclear force operate?