 |  Biology, 6/e Author Dr. George B. Johnson,
Washington University
Author Dr. Peter H. Raven,
Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer,
Carleton College
Contributor Dr. Jonathan Losos,
Washington University
The Nature of Molecules
Answers to Review Questions| Chapter 2 (p. 34)
1. The atomic number = 7, atomic mass = 14, number of electrons = 7.
2. Isotopes are atoms of the same element with a different number of neutrons (and therefore a different weight). Many isotopes are unstable and tend to decay at a constant rate, and are therefore useful in scientific dating techniques.
3. It will contain 8 milligrams and 4 milligrams, respectively. It will take 6660 years.
4. The octet rule states that atoms completely fill outer energy levels. Behavior of atoms both singly and during chemical reactions is strongly influenced by this phenomenon, which accounts for the bonding behavior of most atoms.
5. An ionic bond is formed when electrons from one atom are donated to another; an example is NaCl (sodium chloride). A covalent bond is formed when electron orbitals of two atoms overlap such that electrons are shared between the two atoms; an example is H2O (water).
6. Oxygen and hydrogen atoms contribute to the formation of hydrogen bonds. Slightly electronegative oxygen regions of molecules (usually water) are attracted to the slightly electropositive hydrogen atoms, polarizing the molecules in a specific way. Water has a high specific heat because a lot of thermal energy is required to disrupt the hydrogen bonding in water to raise its temperature.
7. Hydrophobic molecules are nonpolar molecules that will not readily form hydrogen bonds with water, so consequently, will self-associate. Hydrophilic molecules are polar molecules. Hydrophilic molecules do form hydrogen bonds with water.
8. A solution with a hydrogen ion concentration of 10-3 mole/liter would have a pH of 3 and would be acidic.
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2002 McGraw-Hill Higher Education