Chapter 2

State and explain the law of conservation of mass.

State and explain the law of definite proportions.

State and explain the law of multiple proportions. How is the law of multiple proportions different from the law of definite proportions?

What are the main ideas in Dalton's atomic theory? How do they help explain the laws of conservation of mass, of constant composition, and of definite proportions?

Explain Millikan's oil drop experiment and how it led to the measurement of the electron's charge. Why is the magnitude of the charge of the electron so important?

Explain Millikan's oil drop experiment and how it led to the measurement of the electron's charge. Why is the magnitude of the charge of the electron so important?

Describe Rutherford's nuclear model of the atom. What was revolutionary about his model?

If matter is mostly empty space, as suggested by Rutherford, then why does it appear so solid?

List the three subatomic particles that compose atoms and give the basic properties (mass and charge) of each.

What defines an element?

Explain the difference between \(Z\) (the atomic number) and \(A\) (the mass number).

Describe the two different notations used to specify isotopes and give an example of each.

What is an ion? A cation? An anion?

State the periodic law. How did the periodic law lead to the periodic table?

Describe the characteristic properties of metals, nonmetals, and metalloids.

List the characteristic properties of each group. a. noble gases b. alkali metals c. alkaline earth metals d. halogens

Explain how a mass spectrometer works.

What kind of information can be determined from a mass spectrum?

Why is the mass corresponding to a mole of one element different from the mass corresponding to a mole of another element?

A hydrogen-filled balloon is ignited, and \(1.50 \mathrm{~g}\) of hydrogen reacts with \(12.0 \mathrm{~g}\) of oxygen. How many grams of water vapor form? (Assume that water vapor is the only product.)

Two samples of sodium chloride are decomposed into their constituent elements. One sample produces \(6.98 \mathrm{~g}\) of sodium and \(10.7 \mathrm{~g}\) of chlorine, and the other sample produces \(11.2 \mathrm{~g}\) of sodium and \(17.3 \mathrm{~g}\) of chlorine. Are these results consistent with the law of definite proportions? Explain your answer.

Two samples of carbon tetrachloride are decomposed into their constituent elements. One sample produces \(38.9 \mathrm{~g}\) of carbon and \(448 \mathrm{~g}\) of chlorine, and the other sample produces \(14.8 \mathrm{~g}\) of carbon and \(134 \mathrm{~g}\) of chlorine. Are these results consistent with the law of definite proportions? Explain your answer.

Two samples of sodium chloride are decomposed into their constituent elements. One sample produces 6.98 g of sodium and \(10.7 \mathrm{~g}\) of chlorine, and the other sample produces \(11.2 \mathrm{~g}\) of sodium and \(17.3 \mathrm{~g}\) of chlorine. Are these results consistent with the law of definite proportions? Explain your answer.

The mass ratio of sodium to fluorine in sodium fluoride is 1.21:1. A sample of sodium fluoride produces 28.8 g of sodium upon decomposition. How much fluorine (in grams) forms?

Upon decomposition, one sample of magnesium fluoride produces \(1.65 \mathrm{~kg}\) of magnesium and \(2.57 \mathrm{~kg}\) of fluorine. A second sample produces \(1.32 \mathrm{~kg}\) of magnesium. How much fluorine (in grams) does the second sample produce?

Two different compounds containing osmium and oxygen have the following masses of oxygen per gram of osmium: 0.168 and \(0.3369 \mathrm{~g} .\) Show that these amounts are consistent with the law of multiple proportions.

Palladium forms three different compounds with sulfur. The mass of sulfur per gram of palladium in each compound is listed here. Show that these masses are consistent with the law of multiple proportions. $$ \begin{array}{cc} \text { Compound } & \text { Grams } \text { S per Gram Pd } \\ \hline \text { A } & 0.603 \\ \hline \text { B } & 0.301 \\ \hline \text { C } & 0.151 \\ \hline \end{array} $$

Sulfur and oxygen form both sulfur dioxide and sulfur trioxide. When samples of these are decomposed, the sulfur dioxide produces \(3.49 \mathrm{~g}\) oxygen and \(3.50 \mathrm{~g}\) sulfur, while the sulfur trioxide produces \(6.75 \mathrm{~g}\) oxygen and \(4.50 \mathrm{~g}\) sulfur. Calculate the mass of oxygen per gram of sulfur for each sample and show that these results are consistent with the law of multiple proportions.

Sulfur and fluorine form several different compounds including sulfur hexafluoride and sulfur tetrafluoride. Decomposition of a sample of sulfur hexafluoride produces 4.45 g of fluorine and \(1.25 \mathrm{~g}\) of sulfur, while decomposition of a sample of sulfur tetrafluoride produces \(4.43 \mathrm{~g}\) of fluorine and \(1.87 \mathrm{~g}\) of sulfur. Calculate the mass of fluorine per gram of sulfur for each sample and show that these results are consistent with the law of multiple proportions.

Which statements are consistent with Dalton's atomic theory as it was originally stated? Why? a. Sulfur and oxygen atoms have the same mass. b. All cobalt atoms are identical. c. Potassium and chlorine atoms combine in a 1: 1 ratio to form potassium chloride. d. Lead atoms can be converted into gold.

A chemist in an imaginary universe, where electrons have a different charge than they do in our universe, performs the Millikan oil drop experiment to measure the electron's charge. The charges of several drops are recorded here. What is the charge of the electron in this imaginary universe? $$ \begin{array}{cc} \text { Drop number } & \text { Charge } \\ \hline \text { A } & -6.9 \times 10^{-19} \mathrm{C} \\ \hline \text { B } & -9.2 \times 10^{-19} \mathrm{C} \\ \hline \text { C } & -11.5 \times 10^{-19} \mathrm{C} \\ \hline \text { D } & -4.6 \times 10^{-19} \mathrm{C} \\ \hline \end{array} $$

A chemist in an imaginary universe, where electrons have a different charge than they do in our universe, performs the Millikan oil drop experiment to measure the electron's charge. The charges of several drops are recorded here. What is the charge of the electron in this imaginary universe? $$ \begin{array}{cc} \text { Drop number } & \text { Charge } \\ \hline \text { A } & -4.8 \times 10^{-9} \mathrm{z} \\ \hline \text { B } & -9.6 \times 10^{-9} \mathrm{z} \\ \hline \text { C } & -6.4 \times 10^{-9} \mathrm{z} \\ \hline \text { D } & -12.8 \times 10^{-9} \mathrm{z} \\ \hline \end{array} $$

On a dry day, your body can accumulate static charge from walking across a carpet or from brushing your hair. If your body develops a charge of \(-15 \mu\) C (microcoulombs), how many excess electrons has it acquired? What is their collective mass?

How many electrons are necessary to produce a charge of \(-1.0 \mathrm{C} ?\) What is the mass of this many electrons?

Write isotopic symbols in the form \(X-A\) (e.g., \(C-13\) ) for each isotope. a. the silver isotope with 60 neutrons b. the silver isotope with 62 neutrons c. the uranium isotope with 146 neutrons d. the hydrogen isotope with one neutron

Write isotopic symbols in the form \(\frac{A}{Z} \mathrm{X}\) for each isotope. a. the copper isotope with 34 neutrons b. the copper isotope with 36 neutrons c. the potassium isotope with 21 neutrons d. the argon isotope with 22 neutrons

Determine the number of protons and the number of neutrons in each isotope. a. \({ }_{7}^{14} \mathrm{~N}\) b. \(\frac{23}{11} \mathrm{Na}\) c. \(\frac{222}{86} \mathrm{Rn}\) d. \(\frac{208}{82} \mathrm{Pb}\)

The amount of carbon- 14 in ancient artifacts and fossils is often used to establish their age. Determine the number of protons and the number of neutrons in carbon-14 and write its symbol in the form \({ }_{Z}^{A} \mathrm{X}\).

Uranium-235 is used in nuclear fission. Determine the number of protons and the number of neutrons in uranium- 235 and write its symbol in the form \({ }_{Z}^{A} \mathrm{X}\).

Determine the number of protons and the number of electrons in each ion. a. \(\mathrm{Al}^{3+}\) b. \(\mathrm{Se}^{2-}\) c. \(\mathrm{Ga}^{3+}\) d. \(\mathrm{Sr}^{2+}\)

Predict the charge of the ion formed by each element. a. \(\mathrm{Mg}\) b. \(\mathrm{N}\) c. \(\mathrm{F}\) d. \(\mathrm{Na}\)

Write the name of each element and classify it as a metal, nonmetal, or metalloid. a. K b. Ba c. I d. O e. Sb

Write the symbol for each element and classify it as a metal, nonmetal, or metalloid. a. gold b. fluorine c. sodium d. tin e. argon

Determine whether or not each element is a main-group element. a. tellurium b. potassium c. vanadium d. manganese

Determine whether or not each element is a transition element. a. \(\mathrm{Cr}\) b. Br c. Mo d. Cs

Classify each element as an alkali metal, alkaline earth metal, halogen, or noble gas. a. sodium b. iodine c. calcium d. barium e. krypton

Classify each element as an alkali metal, alkaline earth metal, halogen, or noble gas. a. F b. Sr c. \(\mathrm{K}\) d. Ne e. At

Which pair of elements do you expect to be most similar? Why? a. \(\mathrm{N}\) and \(\mathrm{Ni}\) b. Mo and Sn c. Na and Mg d. \(\mathrm{Cl}\) and \(\mathrm{F}\) e. \(\mathrm{Si}\) and \(\mathrm{P}\)

The atomic mass of fluorine is 18.998 amu, and its mass spectrum shows a large peak at this mass. The atomic mass of chlorine is 35.45 amu, yet the mass spectrum of chlorine does not show a peak at this mass. Explain the difference.

An element has two naturally occurring isotopes. Isotope 1 has a mass of 120.9038 amu and a relative abundance of \(57.4 \%\), and isotope 2 has a mass of 122.9042 amu. Find the atomic mass of this element and identify it.