Chapter 2

A charged particle moves between two electrically charged plates, as shown here.\(\begin{array}{l}{\text { (a) What is the sign of the electrical charge on the particle? }} \\ {\text { (b) As the charge on the plates is increased, would you ex- }} \\ {\text { pect the bending to increase, decrease, or stay the same? }}\end{array}$$\begin{array}{l}{\text { (c) As the mass of the particle is increased while the speed of }} \\ {\text { the particles remains the same, would you expect the bending }} \\ {\text { to increase, decrease, or stay the same? [Section } 2.2 ]}\end{array}\)

A 1.0 -g sample of carbon dioxide \(\left(\mathrm{CO}_{2}\right)\) is fully decomposed into its elements, yielding 0.273 g of carbon and 0.727 \(\mathrm{g}\) of oxygen. (a) What is the ratio of the mass of \(\mathrm{O}\) to \(\mathrm{C} ?\) (b) If a sample of a different compound decomposes into 0.429 \(\mathrm{g}\) of carbon and 0.571 \(\mathrm{g}\) of oxygen, what is its ratio of the mass of \(\mathrm{O}\) to \(\mathrm{C} ?(\mathbf{c})\) According to Dalton's atomic theory, what is the empirical formula of the second compound?

Hydrogen sulfide is composed of two elements: hydrogen and sulfur. In an experiment, 6.500 g of hydrogen sulfide is fully decomposed into its elements. (a) If 0.384 g of hydrogen is obtained in this experiment, how many grams of sulfur must be obtained? (b) What fundamental law does this experiment demonstrate?

A chemist finds that 30.82 gof nitrogen will react with 17.60 , \(35.20,70.40,\) or 88.00 g of oxygen to form four different compounds. (a) Calculate the mass of oxygen per gram of nitrogen in each compound. (b) How do the numbers in part (a) support Dalton's atomic theory?

In a series of experiments, a chemist prepared three different compounds that contain only iodine and fluorine and determined the mass of each element in each compound:(a) Calculate the mass of fluorine per gram of iodine in each compound. (b) How do the numbers in part (a) support the atomic theory?

Which of the three subatomic particles was discovered first- the proton, neutron, or electron? Which one was discovered last?

What fraction of the \(\alpha\) particles in Rutherford's gold foil experiment are scattered at large angles? Assume the gold foil is two layers thick, as shown in Figure \(2.9,\) and that the approximate diameters of a gold atom and its nucleus are 2.7 A and \(1.0 \times 10^{-4} \hat{\mathrm{A}}\) , respectively. Hint: Calculate the cross sectional area occupied by the nucleus as a fraction of that occupied by the atom. Assume that the gold nuclei in each layer are offset from each other.

The radius of an atom of gold (Au) is about 1.35 \(\mathrm{A}\) .(a) Express this distance in nanometers \((\mathrm{nm})\) and in picometers \((\mathrm{pm}) .\) (b) How many gold atoms would have to be lined up to span 1.0 \(\mathrm{mm}\) ? (c) If the atom is assumed to be a sphere,what is the volume in \(\mathrm{cm}^{3}\) of a single Au atom?

An atom of rhodium (Rh) has a diameter of about \(2.7 \times 10^{-8} \mathrm{cm} .\) (a) What is the radius of a rhodium atom in angstroms (A) and in meters \((\mathrm{m}) ?\) (b) How many Rh atoms would have to be placed side by side to span a distance of 6.0\(\mu \mathrm{m}\) ? (c) If you assume that the Rh atom is a sphere, what is the volume in \(\mathrm{m}^{3}\) of a single atom?

Answer the following questions without referring to Table \(2.1 :\) (a) What are the main subatomic particles that make up the atom? (b) What is the relative charge (in multiples of the electronic charge ) of each of the particles? (c) Which of the particles is the most massive? (d) Which is the least massive?

Determine whether each of the following statements is true or false. If false, correct the statement to make it true: (a) The nucleus has most of the mass and comprises most of the volume of an atom. (b) Every atom of a given element has the same number of protons.(c) The number of electrons in an atom equals the number of neutrons in the atom. (d) The protons in the nucleus of the helium atom are held together by a force called the strong nuclear force.

Consider an atom of 10 \(\mathrm{B}\) . (a) How many protons, neutrons, and electrons does this atom contain? (b) What is the symbol of the atom obtained by adding one proton to \(^{10} \mathrm{B} ?\) (c) What is the symbol of the atom obtained by adding one neutron to 10 \(\mathrm{B}\) ? (c) What is the symbol of the atom obtained by adding one neutron to 10 \(\mathrm{B} ?(\mathbf{d})\) Are either of the atoms obtained in parts (b) and (c) isotopes of 10 \(\mathrm{B} ?\) If so which one?

Consider an atom of \(^{63} \mathrm{Cu}\) (a) How many protons, neutrons, and electrons does this atom contain? (b) What is the symbol of the ion obtained by removing two electrons from 63 \(\mathrm{Cu} ?(\mathbf{c})\) What is the symbol for the isotope of \(^{63} \mathrm{Cu}\) that possesses 36 neutrons?

(a) Define atomic number and mass number. (b) Which of these can vary without changing the identity of the element?

(a) Which two of the following are isotopes of the same element: \(\frac{31}{16} \mathrm{X}, \frac{31}{15} \mathrm{X}, \frac{32}{16} \mathrm{X}\) ? (b) What is the identity of the element whose isotopes you have selected?

How many protons, neutrons, and electrons are in the following atoms? (a) \(^{40} \mathrm{Ar},(\mathbf{b})^{65} \mathrm{Zn},(\mathbf{c})^{70} \mathrm{Ga},(\mathbf{d})^{80} \mathrm{Br},(\mathbf{e})^{184} \mathrm{W}\) \((\mathbf{f})^{243} \mathrm{Am} .\)

Each of the following isotopes is used in medicine. Indicate the number of protons and neutrons in each isotope: (a) phosphorus-32,(b) chromium-51, (c) cobalt--60, (d) technetium-99, (e) iodine-131, (f) thallium-201.

Write the correct symbol, with both superscript and subscript, for each of the following. Use the list of elements in the front inside cover as needed: (a) the isotope of platinum that contains 118 neutrons, \((\mathbf{b})\) the isotope of krypton with mass number \(84,(\mathbf{c})\) the isotope of arsenic with mass number \(75,(\mathbf{d})\) the isotope of magnesium that has an equal number of protons and neutrons.

One way in which Earth's evolution as a planet can be understood is by measuring the amounts of certain isotopes in rocks. One quantity recently measured is the ratio of 1129 \(\mathrm{Xe}\) to \(^{130} \mathrm{Xe}\) in some minerals. In what way do these two isotopes differ from one another? In what respects are they the same?

(a) What isotope is used as the standard in establishing the atomic mass scale? (b) The atomic weight of boron is reported as 10.81 , yet no atom of boron has the mass of 10.81 amu. Explain.

(a) What is the mass in amu of a carbon-12 atom? (b) Why is the atomic weight of carbon reported as 12.011 in the table of elements and the periodic table in the front inside cover of this text?

Only two isotopes of copper occur naturally: 63 Cu (atomic mass \(=62.9296\) amu; abundance 69.17\(\%\) and 65 (atomic mass \(=64.9278\) amu; abundance 30.83\(\%\) ). Calculate the atomic weight (average atomic mass) of copper.

Rubidium has two naturally occurring isotopes, rubidium-85 (atomic mass \(=84.9118\) amu; abundance \(=72.15 \%\) ) and rubidium-87 (atomic mass = 86.9092 amu; abundance = 27.85\(\%\) ). Calculate the atomic weight of rubidium.

Mass spectrometry is more often applied to molecules than to atoms. We will see in Chapter 3 that the molecular weight of a molecule is the sum of the atomic weights of the atoms in the molecule. The mass spectrum of \(\mathrm{H}_{2}\) is taken under conditions that prevent decomposition into \(\mathrm{H}\) atoms.The two naturally occurring isotopes of hydrogen are \(^{1} \mathrm{H}\) (atomic mass \(=1.00783\) amu; abundance 99.9885\(\% )\) and 2H (atomic mass \(=2.01410\) amu; abundance 0.0115\(\% ) .\) (a) How many peaks will the mass spectrum have? (b) Give the relative atomic masses of each of these peaks. (c) Which peak will be the largest, and which the smallest?

For each of the following elements, write its chemical symbol, locate it in the periodic table, give its atomic number, and indicate whether it is a metal, metalloid, or nonmetal: (a) chromium, (b) helium, (c) phosphorus, (d) zinc, (e) magnesium, (f) bromine, (g) arsenic.

Locate each of the following elements in the periodic table; give its name and atomic number, and indicate whether it is a metal, metalloid, or nonmetal: (a) \(\mathrm{Li},(\mathbf{b}) \mathrm{Sc},(\mathbf{c}) \mathrm{Ge},(\mathbf{d}) \mathrm{Yb}\) \((\mathbf{e}) \mathrm{Mn},(\mathbf{f}) \mathrm{Sb},(\mathbf{g}) \mathrm{Xe}\)

For each of the following elements, write its chemical symbol, determine the name of the group to which it belongs (Table \(2.3 ),\) and indicate whether it is a metal, metalloid, or nonmetal: (a) potassium, (b) iodine, (c) magnesium, (d) argon, (e) sulfur.

The elements of group 4 \(\mathrm{A}\) show an interesting change in properties moving down the group. Give the name and chemical symbol of each element in the group and label it as a nonmetal, metalloid, or metal.

The structural formulas of the compounds \(n\) -butane and isobutane are shown below.(a) Determine the molecular formula of each.(b) Determine the empirical formula of each. (c) Which formulas - empirical, molecular, or structural- allow you determine these are different compounds?

Two substances have the same molecular and empirical formulas. Does this mean that they must be the same compound?

Write the empirical formula corresponding to each of the following molecular formulas: (a) \(\mathrm{Al}_{2} \mathrm{Br}_{6},(\mathbf{b}) \mathrm{C}_{8} \mathrm{H}_{10}\) (c) \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2},(\mathbf{d}) \mathrm{P}_{4} \mathrm{O}_{10},(\mathbf{e}) \mathrm{C}_{6} \mathrm{H}_{4} \mathrm{Cl}_{2},(\mathbf{f}) \mathrm{B}_{3} \mathrm{N}_{3} \mathrm{H}_{6} .\)

Determine the molecular and empirical formulas of the following: (a) the organic solvent benzene, which has six carbon atoms and six hydrogen atoms; (b) the compound silicon tetrachloride, which has a silicon atom and four chlorine atoms and is used in the manufacture of computer chips; (c) the reactive substance diborane, which has two boron atoms and six hydrogen atoms; (d) the sugar called glucose, which has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.

How many hydrogen atoms are in each of the following: (a) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH},(\mathbf{b}) \mathrm{Ca}\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{COO}\right)_{2},(\mathbf{c})\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4} ?\)

How many of the indicated atoms are represented by each chemical formula: (a) carbon atoms in \(\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{COOCH}_{3}\) (b) oxygen atoms in \(\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2},(\mathbf{c})\) hydrogen atoms in \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4} ?\)

Each of the following elements is capable of forming an ion in chemical reactions. By referring to the periodic table, predict the charge of the most stable ion of each: (a) Mg, (b) Al, \((\mathbf{c}) \mathrm{K},(\mathbf{d}) \mathrm{S},(\mathbf{e}) \mathrm{F}\)

Using the periodic table, predict the charges of the ions of the following elements: (a) Ga, (b) Sr, (c) As, (d) Br, (e) Se.

Using the periodic table to guide you, predict the chemical formula and name of the compound formed by the following elements: \((\mathbf{a})\) Ga and \(\mathrm{F},(\mathbf{b})\) Li and \(\mathrm{H},(\mathbf{c})\) Al and \(\mathrm{I},(\mathbf{d}) \mathrm{K}\) and \(\mathrm{S}\)

The most common charge associated with scandium in its compounds is \(3+.\) Indicate the chemical formulas you would expect for compounds formed between scandium and (a) iodine, ( b) sulfur, (c) nitrogen.

Predict the chemical formula for the ionic compound formed by (a) \(\mathrm{Ca}^{2+}\) and \(\mathrm{Br}^{-},(\mathbf{b}) \mathrm{K}^{+}\) and \(\mathrm{CO}_{3}^{2-},(\mathbf{c}) \mathrm{Al}^{3+}\) and \(\mathrm{CH}_{3} \mathrm{COO}^{-},(\mathbf{d}) \mathrm{NH}_{4}^{+}\) and \(\mathrm{SO}_{4}^{2-},(\mathbf{e}) \mathrm{Mg}^{2+}\) and \(\mathrm{PO}_{4}^{3-}\) .

Predict the chemical formulas of the compounds formed by the following pairs of ions: (a) \(\mathrm{Cr}^{3+}\) and \(\mathrm{Br}^{-},\) (b) \(\mathrm{Fe}^{3+}\) and \(\mathrm{O}^{2-}\) , \((\mathbf{c}) \mathrm{Hg}_{2}^{2+}\) and \(\mathrm{CO}_{3}^{2-},(\mathbf{d}) \mathrm{Ca}^{2+}\) and \(\mathrm{ClO}_{3}^{-},(\mathbf{e}) \mathrm{NH}_{4}^{+}\) and \(\mathrm{PO}_{4}^{3-}\).

Predict whether each of the following compounds is molecular or ionic: (a) \(\mathrm{B}_{2} \mathrm{H}_{6},(\mathbf{b}) \mathrm{CH}_{3} \mathrm{OH},(\mathbf{c}) \mathrm{LiNO}_{3},(\mathbf{d}) \mathrm{Sc}_{2} \mathrm{O}_{3}\) (e) \(\mathrm{CsBr},(\mathbf{f}) \mathrm{NOCl},(\mathbf{g}) \mathrm{NF}_{3},(\mathbf{h}) \mathrm{Ag}_{2} \mathrm{SO}_{4}\)

Which of the following are ionic, and which are molecular? (a) \(\mathrm{PF}_{5},(\mathbf{b}) \mathrm{NaI},(\mathbf{c}) \mathrm{SCl}_{2},(\mathbf{d}) \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2},(\mathbf{e}) \mathrm{FeCl}_{3},(\mathbf{f}) \mathrm{LaP}\) \((\mathrm{g}) \mathrm{CoCO}_{3},(\mathbf{h}) \mathrm{N}_{2} \mathrm{O}_{4}\)

Give the chemical formula for (a) chlorite ion, (b) chloride ion, (c) chlorate ion, (d) perchlorate ion, (e) hypochlorite ion.

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

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

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

Name the following ionic compounds: (a) \(\mathrm{Li}_{2} \mathrm{O},(\mathbf{b})\) FeCl_ \((\mathbf{c}) \mathrm{NaClO},(\mathbf{d}) \quad \mathrm{CaSO}_{3}\)(e) \(\mathrm{Cu}(\mathrm{OH})_{2}, \quad(\mathbf{f}) \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}$$(\mathbf{g}) \mathrm{Ca}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2},(\mathbf{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) \(\mathrm{KCN},(\mathbf{b})\mathrm{NaBrO}_{2}\) \((\mathbf{c}) \operatorname{Sr}(\mathrm{OH})_{2}, \quad(\mathbf{d}) \quad\) CoTe (e) \(\mathrm{Fe}_{2}\left(\mathrm{CO}_{3}\right)_{3}, \quad(\mathbf{f}) \quad \mathrm{Cr}\left(\mathrm{NO}_{3}\right)_{3}$$(\mathrm{g})\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{3},(\mathbf{h}) \mathrm{NaH}_{2} \mathrm{PO}_{4}$$(\mathbf{i}) \mathrm{KMnO}_{4},(\mathrm{i}) \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, ( \(\mathbf{d} )\) zinc nitrate, (e) mercury(II) bromide, (f) iron(III) carbonate, (g) sodium hypobromite.

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