Chapter 4

Does the existence of isotopes contradict part of Dalton’s original atomic theory? Explain.

How many protons and electrons are contained in an atom of element 44?

Carbon A carbon atom has a mass number of 12 and an atomic number of 6. How many neutrons does it have?

Mercury An isotope of mercury has 80 protons and 120 neutrons. What is the mass number of this isotope?

Xenon An isotope of xenon has an atomic number of 54 and contains 77 neutrons. What is the xenon isotope’s mass number?

If an atom has 18 electrons, how many protons does it have?

How many electrons, protons, and neutrons are contained in each atom? a. \(\quad \stackrel{132}{55} \mathrm{Cs}\) b. \(\quad \stackrel{59}{27} \mathrm{Co}\) c. \(\quad \stackrel{163}{69} \mathrm{Tm}\) d. \(\quad \stackrel{70}{30} \mathrm{Zn}\)

For each chemical symbol, determine the number of protons and electrons an atom of the element contains. \(\begin{array}{ll}{\text { a. } V} & {\text { c. Ir }} \\ {\text { b. Mn }} & {\text { d. } S}\end{array}\)

Gallium, which has an atomic mass of 69.723 amu, has two naturally occurring isotopes, Ga-69 and Ga-71. Which isotope occurs in greater abundance? Explain.

Atomic Mass of Silver Silver has two isotopes: \(\stackrel{107}{47} \mathrm{Ag}\), which has a mass of 106.905 amu and a percent abundance of \(52.00 \%,\) and \(\stackrel{109}{47} \mathrm{Ag}\) which has a mass of 108.905 amu and an percent abundance of 48.00\(\%\) What is the atomic mass of silver?

Why are some atoms radioactive?

Discuss how radioactive atoms gain stability

Define alpha particle, beta particle, and gamma ray.

Write the symbols used to denote alpha, beta, and gamma radiation and give their mass and charge.

What type of reaction involves changes in the nucleus of an atom?

Radioactive Emissions What change in mass number occurs when a radioactive atom emits an alpha particle? A beta particle? A gamma particle?

What is the primary factor that determines whether an nucleus is stable or unstable?

Explain how energy loss and nuclear stability are related to radioactive decay.

Explain what must occur before a radioactive atom stops to undergo further radioactive decay.

Boron-10 emits alpha particles and cesium-137 emits beta particles. Write balanced nuclear reactions for each radioactive decay.

Determine what was wrong with Dalton’s theory and provide the most recent version of the atomic structure.

Cathode-Ray Tube Describe a cathode-ray tube and how it operates.

Subatomic Particles Explain how J. J. Thomson’s determination of the charge- to-mass ratio of the electron led to the conclusion that atoms were composed of subatomic particles.

Gold Foil Experiment How did the actual results of Rutherford’s gold foil experiment differ from the results he expected?

If a nucleus contains 12 protons, how many electrons are in the neutral atom? Explain.

An atom’s nucleus has 92 protons and its mass number is 235. How many neutrons are in the nucleus? What is the name of the atom?

Approximately how many times greater is the diameter of an atom than the diameter of its nucleus? Knowing that most of an atom’s mass is contained in the nucleus, what can you conclude about the density of the nucleus?

Is the charge of a nucleus positive, negative, or zero? The charge of an atom?

Why are electrons in a cathode-ray tube deflected by electric fields?

What was Henry Moseley’s contribution to the modern understanding of the atom?

What is the mass number of potassium-39? What is the isotope’s charge?

Boron-10 and boron-11 are the naturally occurring isotopes of elemental boron. If boron has an atomic mass of 10.81 amu, which isotope occurs in greater abundance?

Semiconductors Silicon is important to the semiconductor manufacturing industry. The three naturally occuring isotopes of silicon are silicon-28, silicon-29, and silicon-30. Write the symbol for each.

Describe how each type of radiation affects an atom’s atomic number and mass number.

Relative Abundances Magnesium constitutes about 2\(\%\) of Earth's crust and has three naturally occurring isotopes. Suppose you analyze a mineral and determine that it contains the three isotopes in the following proportions: Mg-24 (abundance \(=79 \%\) ), Mg-25 (abundance \(=10 \%\) ) and \(\mathrm{Mg}-26\) (abundance \(=11 \%\) . If your friend analyzes a different mineral containing magnesium, do you expect her to obtain the same relative abundances for each magnesium isotope? Explain your reasoning.

Formulate How were scientific methods used to determine the model of the atom? Why is the model considered a theory?

Discuss What experiment led to the dispute of J. J. Thomson’s plum pudding atomic model? Explain your answer.

Apply If atoms are primarily composed of empty space, explain why you cannot pass your hand through a solid object.

Formulate Sketch a modern atomic model of a typical atom and identify where each type of subatomic particle would be located.

Apply Indium has two naturally occurring isotopes and an atomic mass of 114.818 amu. In-11 3 has a mass of 112.904 amu and an abundance of 4.3\(\% .\) What is the identity and percent abundance of indium's other isotope?

Infer Sulfur’s average atomic mass is close to the whole number 32. Chlorine’s average atomic mass is 35.453, which is not a whole number. Suggest a possible reason for this difference.

Magnesium Isotopes Compute the mass number, \(X,\) of the third isotope of magnesium given that the respective abundances of the naturally occurring isotopes are: \(79.0 \%, 10 \%,\) and 11\(\%\) for \(_{12}^{24} \mathrm{Mg}\) \(\underset{12}{25} \mathrm{Mg}, \underset{12}{X} \mathrm{Mg}\) The relative atomic mass of magnesium is 24.305 amu.

How is a qualitative observation different from a quantitative observation? Give an example of each. (Chapter 1)

\(\mathrm{A} 1.0 \mathrm{cm}^{3}\) block of gold can be flattened to a thin sheet that averages \(3.0 \times 10^{-8} \mathrm{cm}\) thick. What is the area (in \(\mathrm{cm} 2 )\) of the flattened gold sheet? (Chapter 2 )

Classify each mixture as heterogeneous or homogeneous. (Chapter 3) a. salt water b. vegetable soup c. \(14-\mathrm{Kgold}\) d. concrete

Determine whether each change is physical or chemical. (Chapter 3) a. Water boils. b. A match burns. c. Sugar dissolves in water. d. Sodium reacts with water. e. Ice cream melts

Television and Computer Screens Describe how cathode rays are used to generate television and computer monitor images.

The Standard Model The standard model of particle physics describes all of the known building blocks of matter. Research the particles included in the standard model. Write a short report describing the known particles and those thought to exist but not yet detected experimentally.

Does the number of protons or neutrons remain the same for all isotopes? Explain.