Chapter 3 - Atoms: The Building Blocks of Matter

3.1 The Atom: From Philosophical Idea to Scientific Theory

1. Describe the major contributions of each of the following to the modern theory of the atom:
a) Democritus
b) John Dalton

2. List the five essential points of Dalton's atomic theory.

3. Explain each of the following in terms of Dalton's atomic theory:
a) the law of conservation of mass
b) the law of definite proportions
c) the law of multiple proportions

4. According to the law of conservation of mass, if element A has an atomic mass of two mass units and element B has an atomic mass of three mass units, what mass would be expected for
a) compound AB
b) compound A2B3


3.2 The Structure of the Atom

1. Define each of the following:
a) atom
b) electron
c) nucleus
d) proton
e) neutron

2. Describe one conclusion made by each of the following scientists that led to the development of the current atomic theory:
a) Thomson
b) Millikan
c) Rutherford

3. Prepare a table listing the three subatomic particles in column one, in column two indicate the location in the atom for each particle, in column three indicate the mass of each particle, in column four indicate the relative charge of each particle.

4. Why is the cathode-ray tube in Figure 3-4 connected to a vacuum pump?

5. Draw a cathode ray tube and
a) indicate the anode and the cathode
b) indicate the charge of the cathode and the anode
c) indicate why each has the charge it does

6. a) Define atom
b) What are the two regions in the atom?

7. Summarize Rutherford's model of an atom, and explain how he developed this model based on the results of his famous gold-foil experiment.

8. What one thing conclusively identifies an element?

3.3 Counting Atoms

1. What is the mass in grams of 7.5 x 1015 atoms of nickel, Ni? Show given information, formula, plug into formula, cancellation of units, and follow the rules for significant figures. (7.3 x 10-7 g Ni) soln

2. How many atoms of sulfur, S, are in 4.00 g of sulfur? Show given information, formula, plug into formula, cancellation of units, and follow the rules for significant figures. (7.51 x 10-22 atoms S) soln

3. What mass of gold, Au, Contains the same number of atoms as 9.0 g of aluminum, Al? Show given information, formula, plug into formula, cancellation of units, and follow the rules for significant figures. (66 g Au) soln

4. For each of the following, indicate the number of protons, electrons, and neutrons and show all work:
a) sodium-23
b) calcium-40
c) 2964 g Cu
d) 47108 g Ag

5. Write the nuclear symbol and hyphen notation for each of the following isotopes:
a) mass number of 28 and atomic number of 14
b) 26 protons and 30 neutrons
c) 56 electrons and 82 neutrons

6. To two decimal places, what is the relative atomic mass and the molar mass of the element potassium, K?

7. Determine the mass in grams of the following, showing given information, unit cancellation, and follow the rules of significant figures:
a) 2.00 mol N (28.0 g N) soln
b) 3.01 x 1023 atoms Cl (17.8 g Cl) soln

8. Determine the amount in moles of the following, showing given information, unit cancellation, and follow the rules of significant figures:
a) 12.15 g Mg (0.5000 mol Mg) soln
b) 1.50 x 1023 atoms F (0.249 mol F) soln

9. Determine the number of atoms in the following, showing given information, unit cancellation, and follow the rules of significant figures:
a) 2.50 mol Zn (1.50 x 1024 atoms Zn) soln
b) 1.50 g C (7.52 x 1022 atoms C) soln

10. a) Define isotope.
b) How are the isotopes of an element alike?
c) How are the isotopes of an element different?

11. Define nuclide.

12. Define the molar mass of an element.