Biology: Life on Earth 7e
Student Self Test Questions and Answers
Chapter 2: Atoms, Molecules, and Life
Self Test
1. The basic structural units of chemistry and life are __________.
a. atoms
b. electrons
c. protons
d. neutrons
e. molecules
2. The atomic number of carbon is 6. A carbon atom has __________ protons and __________ electrons.
a. 3, 3
b. 6, 6
c. 6, 12
d. 6, 3
3. Ions are atoms that have __________.
a. different numbers of neutrons
b. broken apart due to radioactive decay
c. gained an electron
d. lost an electron
e. gained or lost an electron
4. Chemical bonds __________.
a. are interactions between the outermost electron shells of atoms
b. result when atoms share one or more electrons
c. result when atoms gain or lose one or more electrons
d. are the forces that hold atoms together in molecules
5. Ionic bonds form between atoms that have __________.
a. empty outermost electron shells
b. full outermost electron shells
c. nearly empty and nearly full outermost electron shells
d. equal numbers of protons
e. equal numbers of neutrons
6. Covalent bonds __________.
a. are interactions between the outermost electron shells of atoms
b. result when atoms share one or more electrons
c. result when atoms gain or lose one or more electrons
d. are the forces that hold atoms together in molecules such as water
e. all of the above
f. all but one of the above
7. Chemical reactions __________.
a. are interactions between the outermost electron shells of atoms
b. result when atoms share one or more electrons
c. result when atoms gain or lose one or more electrons
d. are the forces that hold atoms together in molecules
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
e. all of the above
f. all but one of the above
8. How many single covalent bonds can the phosphorus atom form?
a. 1
b. 2
c. 3
d. 6
e. 8
9. Nonpolar covalent bonds are different from polar covalent bonds because __________.
a. electrons are shared unequally in nonpolar covalent bonds and are shared equally in polar
covalent bonds
b. electrons are shared equally in nonpolar covalent bonds and are shared unequally in polar
covalent bonds
c. electrons are lost in nonpolar covalent bonds and are gained in polar covalent bonds
d. electrons are shared in nonpolar covalent bonds and are lost or gained in polar covalent bonds
10. Why is water so essential for life? Read all the choices carefully before selecting your answer.
a. Water takes part in many biochemical reactions.
b. Water is a good solvent.
c. Water moderates the effects of temperature.
d. When water freezes, it forms ice that floats.
e. The atoms in water molecules are held together in polar covalent bonds.
f. All of the answers are correct.
11. Oxygen atoms have an atomic number of 8. Neon atoms have 10 electrons. Predict whether or not these atoms
are generally reactive (i.e., can form chemical bonds with other atoms). Explain your answer. (Note that this question
is not asking whether oxygen can react with neon.)
a. Both oxygen and neon are not reactive because their outermost electron orbitals are filled.
b. Both oxygen and neon are reactive because their outermost electron orbitals are not filled.
c. Oxygen is reactive because its outermost electron shell contains 6 electrons (is not filled); neon
is not reactive because its outermost electron shell contains 8 electrons (is filled).
d. Oxygen is not reactive because its outermost electron shell contains 8 electrons (is filled); neon
is reactive because its outermost electron shell contains 2 electrons (is not filled).
12. Which of the following lists of terms is in the correct order of size, going from smallest to largest?
a. electron, proton, atomic nucleus, electron shell, atom, molecule
b. proton, electron, atomic nucleus, electron shell, atom, molecule
c. molecule, atom, electron shell, atomic nucleus, proton, electron
d. atomic nucleus, electron, proton, electron shell, atom, molecule
e. electron, proton, atomic nucleus, electron shell, molecule, atom
13. Why are hydrophobic molecules such as fats and oils unable to dissolve in watery solutions?
a. Water cannot interact with molecules that have polar covalent bonds, such as fats and oils.
b. Water cannot interact with molecules with ionic bonds, such as fats and oils.
c. Water cannot interact with hydrophobic molecules, such as fats and oils, because hydrophobic
molecules form hydrogen bonds with each other, excluding the water.
d. Water molecules form hydrogen bonds with each other, excluding the hydrophobic molecules.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
14. You are waiting backstage for your cue to come onstage when you notice that you are breathing rapidly and
beginning to feel light-headed. As you try to control your anxiety and slow your breathing, you think about what you
learned in your biology class this week and realize that your hyperventilation is changing your blood pH. Explain.
Reminder: Blood pH is maintained by carbonate buffer, which is related to the amount of CO 2 you breathe in or out.
One way that your body controls the amount of carbonate in your blood is to change the rate of breathing. When you
breathe out, you remove CO2 and lower the amount of carbonic acid in the blood. As a result, the amount of H + ions
in the blood decreases.
Take your time on this one; relating pH to changes in H+ concentration can be confusing.
a. Rapid breathing decreases my blood’s pH, making it more basic.
b. Rapid breathing decreases my blood’s pH, making it more acidic.
c. Rapid breathing increases the pH of my blood, making it more basic.
d. Rapid breathing increases the pH of my blood, making it more acidic.
15. Imagine that you wanted to make a time capsule in which you would seal important artifacts from your life
(pictures, poems, a lock of your baby hair, etc.), to be opened by your heirs 1000 years from now. To prevent these
artifacts from decaying, you want to fill the capsule with a gas that would be least reactive. Which of these gases
would you choose: oxygen gas (O2); carbon dioxide (CO2); argon gas (Ar); hydrogen gas (H2). (The atomic numbers
of the atoms in these molecules are: oxygen = 8; carbon = 6; hydrogen = 2; and argon = 18.)
a. oxygen gas
b. carbon dioxide
c. argon gas
d. hydrogen gas
16. Atoms are the basic building block of elements. Each atom, and therefore the elements themselves, are made up
of subatomic bits of matter that are electrically negative (electrons), electrically positive (protons), and electrically
neutral or uncharged (neutrons). Which subatomic component defines (characterizes) the fundamental nature of each
element?
a. electrons
b. protons
c. neutrons
d. isotopes
17. What allows one atom to physically interact with a second atom?
a. properties of both nuclei
b. properties of the electrons
c. electron shells of both atoms
d. external energy sources
18. One atom can form a chemical bond with a second atom as a result of __________.
a. both atoms possessing incompletely filled outer electron shells
b. both atoms possessing completely filled outer electron shells
c. both atoms possessing empty outer electron shells
d. all of the above
19. Covalent bonds __________.
a. are strong compared to ionic bonds or hydrogen bonds
b. share electrons with another atom
c. may involve the unequal sharing of electrons between two atoms
d. all of the above
20. Water's ability to act as a "universal" solvent is due to __________.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
a. the fact that there is so much of it in the world around us and in our own bodies
b. its natural ability to interact with polar molecules such as ions and proteins
c. the nature of oxygen, which pulls the hydrogen electrons a little closer to it than they are to the
two hydrogen atoms
d. both the second and third answers above
21. Why does water so greatly resist increases in temperature?
a. It takes great energy to break the ionic bonds that hold water molecules together.
b. It takes great energy to break the covalent bonds that hold water molecules together.
c. It takes great energy to break the huge number of hydrogen bonds that hold water molecules
together.
d. none of the above
22. A solution of pH 7 has ________ times _________ H+ ions than a solution of pH 9.
a. 100; fewer
b. 100; more
c. 2; fewer
d. 2; more
23. Which of the following is not a subatomic particle?
a. proton
b. neutron
c. ion
d. electron
24. Which of the following best explains why neon (Ne) atoms would not form bonds with other atoms?
a. Neon atoms have no electrons.
b. Neon has an empty outer shell.
c. The outer shells of neon atoms are completely full with eight electrons.
d. Neon atoms have 7 electrons in their outer shells.
25. The atoms Mg+ and Cl– would most likely be attached to each other by a(n) __________.
a. ionic bond
b. covalent bond
c. hydrogen bond
d. neutral bond
26. The atomic nucleus contains two types of subatomic particles; ____________________ are positively charged
and ____________________ are uncharged.
27. Atoms of the same element with a different number of neutrons are called ____________________.
28. The results of losing, gaining, or sharing electrons are ____________________.
29. Atoms that have gained or lost electrons are called ____________________.
30. Atoms with partially filled outermost electron shells can become stable by sharing electrons with another atom,
forming a ____________________.
31. Ions and polar molecules are termed ____________________ because of their electrical attraction to water;
molecules that are uncharged and nonpolar are called ____________________.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
32. Indicate which of the figures below depict neutral atoms and which depict ions.
33. Identify the electrons, oxygen nucleus, hydrogen nucleus, and type of bond seen in the diagram below.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
34. Below is the pH scale. Indicate which area is acidic, which is basic, and which is neutral.
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