(a) Describe Rutherford's experiment and how the results

Problem 76AP In the facing page of the periodic table at the front of this book is an alphabetical list of elements with atomic masses given to the number of known significant figures. Compare the number of significant figures given for aluminum, bismuth, lead, and molybdenum. Look these elements up on webelements.com and explain why their atomic masses are reported to such different numbers of significant figures.

Problem 1QP Define the terms atom and element.

Problem 2QP Use a familiar macroscopic example as an analogy to describe Dalton’s atomic theory. Explain why a substance such as clay or oil is not useful for an analogy of this type.

Problem 3QP Define the following terms: (a) ? particle, (b) ? particle, (c) ? ray, (d) X ray.

Problem 4QP Name the types of radiation known to be emitted by radioactive elements.

Problem 5QP Compare the properties of the following: ? particles, cathode rays, protons, neutrons, and electrons.

Problem 6QP Describe the contributions of the following scientists to our knowledge of atomic structure: J. J. Thomson, R. A. Millikan, Ernest Rutherford, and James Chadwick.

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

Problem 8QP The diameter of an argon atom is about 2 × 102 pm. If we could line up argon atoms side by side in contact with one another, how many atoms would it take to span a distance of 1 cm?

Problem 9QP The radius of an atom is on the order of 10,000 times as large as its nucleus. If the atom were enlarged such that the radius of its nucleus were 1.0 cm, what would be the radius of the atom in meters, and in miles (1 mi = 1609 m)?

Problem 11QP Why do all atoms of an element have the same atomic number, although they may have different mass numbers?

Problem 12QP What do we call atoms of the same elements with different mass numbers?

Problem 10QP Use the argon-40 isotope to define atomic number and mass number. Why does knowledge of the atomic number enable us to deduce the number of electrons present in an atom?

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

Problem 14QP What is the mass number of an iron atom that has 31 neutrons?

Problem 15QP Calculate the number of neutrons of 239Pu.

Write the appropriate symbol for each of the following isotopes: (a) Z = 11, A = 23; (b) Z = 28, A = 64; (c) Z = 50, A = 115; (d) Z = 20, A = 42.

For each of the following species, determine the number of protons and the number of neutrons in the nucleus: \({ }_{3}^{6 \mathrm{Li},}{ }_{13}^{28} \mathrm{Al},{ }_{13}^{29} \mathrm{Al},{ }_{23}^{50} \mathrm{~V},{ }_{34}^{77} \mathrm{Se},{ }_{77}^{133} \mathrm{Ir} \text {. }\)

Indicate the number of protons, neutrons, and electrons in each of the following species: \({ }_{8}^{77} \mathrm{O},{ }_{14}^{29} \mathrm{Si},{ }_{28}^{58} \mathrm{Ni},{ }_{39}^{89} \mathrm{Y}\), \({ }_{73}^{180} \mathrm{Ta},{ }_{81}^{203} \mathrm{Tl} \text {. }\).

Problem 19QP Write the appropriate symbol for each of the following isotopes: (a) Z = 75, A = 187; (b) Z = 83, A = 209; (c) Z = 33, A = 75; (d) Z = 93, A = 236.

Problem 20QP Determine the mass number of (a) a beryllium atom with 5 neutrons, (b) a sodium atom with 12 neutrons, (c) a selenium atom with 44 neutrons, and (d) a gold atom with 118 neutrons.

Problem 21QP Determine the mass number of (a) a chlorine atom with 18 neutrons, (b) a phosphorus atom with 17 neutrons, (c) an antimony atom with 70 neutrons, and (d) a palladium atom with 59 neutrons.

Problem 22QP The following radioactive isotopes arc used in medicine for imaging organs, studying blood circulation, treating cancer, and so on. Give the number of neutrons present in each isotope: 198Au, 47Ca, 60Co, 18F, l25I, 131I, 42K, 43Na, 35P, 85Sr, 99Tc.

Explain clearly what is meant by the statement "The atomic mass of gold is \(197.0 \mathrm{amu}\)."

Problem 25QP What information would you need to calculate the average atomic mass of an element?

Problem 23QP What is the mass (in amu) of a carbon-12 atom? Why is the atomic mass of carbon listed as 12.01 amu in the table on the inside front cover of this book?

Problem 26QP The atomic masses of (75.78 percent) and (24.22 percent) are 34.969 and 36.966 amu, respectively. Calculate the average atomic mass of chlorine. The percentages in parentheses denote the relative abundances.

Problem 27QP The atomic masses of 204Pb (1.4 percent), 206Pb (24.1 percent), 207Pb (22.1 percent), and 208Pb (52.4 percent) arc 203.973020, 205.974440, 206.975872. and 207.976627, and respectively. Calculate the average atomic mass of lead. The percentages in parentheses denote the relative abundances.

The atomic masses of \({ }^{6} \mathrm{Li} \text { and }{ }^{7} \mathrm{Li}\) are 6.0151 amu and 7.0160 amu, respectively. Calculate the natural abundances of these two isotopes. The average atomic mass of Li is 6.941 amu.

Problem 30QP The element rubidium has two naturally occurring isotopes. The atomic mass of 85Rb (72.17 percent abundant) is 84.911794 amu. Determine the atomic mass of 87Rb (27.83 percent abundant). The average atomic mass of Rb is 85.4678 amu.

Problem 31QP There are three naturally occurring isotopes of the element magnesium. The atomic masses of 25Mg (10.00 percent abundant) and 26Mg (11.01 percent abundant) are 24.9858374 and 25.9825937 amu, respectively. What is the atomic mass of 24Mg (78.99 percent abundant) given the average atomic mass of Mg is 24.3050 amu?

Problem 32QP What is the periodic table, and what is its significance in the study of chemistry?

Problem 28QP The atomic masses of 203Tl and 205Tl are 202.972320 and 204.974401 amu, respectively. Calculate the natural abundances of these two isotopes. To seven significant figures, the average atomic mass of thallium is 204.3833 amu.

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

Give two examples of each of the following: (a) alkali metals, (b) alkaline earth metals, (c) halogens, (d) noble gasses, (e) chalcogens, (f) transition metals.

The explosion of an atomic bomb in the atmosphere releases many radioactive isotopes into the environment. One of the isotopes is \({ }^{90} \mathrm{Sr} \text}\). Via a relatively short food chain, it can enter the human body. Considering the position of strontium in the periodic table, explain why it is particularly harmful to humans.

Problem 36QP Elements whose names end with -ium are usually metals: sodium is one example. Identify a nonmetal whose name also ends with -ium.

Problem 38QP Consult the WebElements Periodic Table of the Elements (http://www.webelements.com) to find (a) two metals less dense than water, (b) two metals more dense than mercury, (c) the densest known solid metallic element, and (d) the densest known solid nonmetallic element.

Problem 37QP 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.

Problem 39QP Group the following elements in pairs that you would expect to show similar properties: K, F, P, Na, Cl, and N.

Problem 40QP Group the following elements in pairs that you would expect to show similar chemical properties: I, Ba, O, Br, S, and Ca.

Problem 42QP Define the term mole. What is the unit for mole in calculations? What does the mole have in common with the dozen and the gross? What does Avogadro’s number represent?

Write the symbol for each of the following biologically important elements in the given periodic table: iron (present in hemoglobin for transporting oxygen), iodine (present in the thyroid gland), sodium (present in intracellular and extracellular fluids), phosphorus (present in bones and teeth), sulfur (present in proteins), and magnesium (present in chlorophyll).

Earth’s population is about 6.8 billion. Suppose that every person on Earth participates in a process of counting identical particles at the rate of two particles per second. How many years would it take to count \(6.0 \times 10^{23}\) particles? Assume that there are 365 days

Problem 45QP The diameter of a human hair is 25.4 µm. If atoms with a diameter of 121 pm were aligned side by side across the hair, how many atoms would be required?

Problem 43QP What is the molar mass of an element? What units are commonly used for molar mass?

Problem 46QP How many atoms are there in 1.60 moles of selenium (Se)?

Problem 47QP How many moles of nickel (Ni) atoms are there in 5.00 × 109 (5 billion) Ni atoms?

Problem 48QP How many moles of strontium (Sr) atoms are in 93.7 g of Sr?

Problem 49QP How many grams of platinum (Pt) are there in 26.4 moles of Pt?

Problem 51QP What is the mass in grams of a single atom of each of the following elements: (a) Sb, (b) Pd?

Problem 50QP What is the mass in grams of a single atom of each of the following elements: (a) Os, (b) Kr?

Problem 52QP What is the mass in grams of 2.00 × 1012 tin (Sn) atoms?

Problem 53QP How many atoms are present in 4.09 g of scandium (Sc)?

Problem 54QP Which of the following has more atoms: 4.56 g of helium atoms or 2.36 g of manganese atoms?

Problem 56AP A sample of a uranium compound is found to be losing mass gradually. Explain what is happening to the sample.

An isotope of a nonmetallic element has mass number 131. An atom of this isotope contains 54 electrons. Write the symbol for this atom

Which of the following has a greater mass: 173 atoms of gold or \(7.5 \times 10^{-22}\) mole of silver?

Problem 60AP Using the information provided in the table, write a symbol for each atom. If there is not enough information, state what additional information is needed to write a correct symbol for that atom. Atom of element A B C D Number of electrons 6 11 29 Number of protons 6 29 36 Number of neutrons 6 7 47

Problem 58AP One isotope of a metallic element has 35 neutrons in the nucleus. The neutral atom has 30 electrons. Write the symbol for this atom.

Problem 61AP Using the information provided in the table, write a symbol for each atom. If there is not enough information, state what additional information is needed to write a correct symbol for that atom. Atom of element A B C D Number of electrons 10 21 50 Number of protons 75 21 50 Number of neutrons 12 110 21

Problem 62AP Which of the following symbols provides more information about the atom: 23Na or 11Na? Explain.

Problem 63AP Discuss the significance of assigning an atomic mass of exactly 12 amu to the carbon-12 isotope.

Problem 64AP 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.)

Problem 66AP The carat is the unit of mass used by jewelers. One carat is exactly 200 mg. How many carbon atoms are present in a 2.5-carat diamond?

Problem 68AP One atom of a particular element with only one naturally occurring isotope has a mass of 3.002 × 10-22 g. What element is this?

Problem 67AP In the geologic record of Earth, the disappearance of the dinosaurs roughly 65 million years ago is marked by a thin line known as the K-T boundary. Because the K-T boundary contains an unusually high concentration of the element iridium, which is ordinarily quite rare in Earth’s crust, geologists have deduced that the mass extinction was caused by the catastrophic impact of an asteroid. The two naturally occurring isotopes of iridium are 191 Ir and l93Ir, with atomic masses of 190.960584 and 192.962917 amu, respectively; and abundances of 37.3 percent and 62.7 percent, respectively. Determine the average atomic mass of iridium and compare your result with the atomic mass given in the periodic table.

Problem 65AP For the noble gases (the Group 8A elements) (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.

Problem 69AP Identify each of the following elements: (a) a halogen containing 53 electrons, (b) a radioactive noble gas with 86 protons, (c) a Group 6A element with 34 electrons, (d) an alkali metal that contains 11 electrons, (e) a Group 4A element that contains 82 electrons.

Problem 71AP While most isotopes of light elements such as oxygen and phosphorus contain relatively equal amounts of protons and neutrons in the nucleus, recent results indicate that a new class of isotopes called neutron-rich isotopes can be prepared. These neutron-rich isotopes push the limits of nuclear stability as the large numbers of neutrons approach the “neutron drip line.” Neutron- rich isotopes may play a critical role in the nuclear processes of stars. Determine the number of neutrons in the following neutron-rich isotopes: (a) 40Mg, (b) 44Si, (c) 48Ca, (d) 43Al.

Fill in the blanks in the table:

Problem 70AP Show the locations of (a) alkali metals, (b) alkaline earth metals, (c) the halogens, and (d) the noble gases in the given outline of a periodic table. Also draw dividing lines between metals and metalloids and between metalloids and nonmetals.

Problem 72AP Fill in the blanks in the table: Symbol Protons 14 Neutrons 15 117 Electrons 79

Problem 74AP (a) Describe Rutherford's experiment and how the results revealed the nuclear structure of the atom. (b) Consider the 23Na atom. Given that the radius and mass of the nucleus arc 3.04 × 10-15 m and 3.82 × 10-23 g, respectively, calculate the density of the nucleus in g/cm3. The radius of a 23Na atom is 186 pm. Calculate the density of the space occupied by the electrons outside the nucleus in the sodium atom. Do your results support Rutherford's model of an atom? [The volume of a sphere of radius r is ]

Problem 75AP 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 arc spherical in shape. Therefore the Pt atoms in the cube cannot fill all 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 Pt is 21.45 g/cm3, and the mass of a single Pt atom is 3.240 × 10-22 g. [The volume of a sphere of radius r is ]