Download Answers to Review Questions

Answers to Review Questions - Chapter 2
1. Do all atoms of an element have the same atomic number? The same atomic
mass? Explain.
Atomic number is based on the number of protons, hence all atoms of a particular
element have the same atomic number. Isotopes vary in the number of neutrons,
hence a different atomic mass.
2. How do ionic and covalent bonds differ?
Ionic bonds involve the gain or loss of electron(s) by 2 or more atoms; covalent bonds
involve the sharing of electron(s) between 2 or more atoms.
3. Describe polar and nonpolar covalent bonds.
Polar covalent bonds have an unequal distribution in the charge of the molecule, so
one region will bear a partial negative charge near the more electronegative atom, and
the other region will bear a partial positive charge near the less electronegative atom.
Nonpolar covalent bonds have equal electron sharing, and thus the molecule has no
regions of electronegativity.
4. Why does water form hydrogen bonds?
Water forms hydrogen bonds, as the water molecule is polar. The electronegative
oxygen atom of the molecule is attracted to the electropositive hydrogen atom of an
adjacent molecule.
5. What are some properties of water that result from hydrogen bonding? How do
these properties contribute to the role of water as an essential component of
organisms?
Because of hydrogen bonding, water exhibits both adhesion and cohesion (capillary
action), important in making water available in soil for plant roots to absorb, and also
playing a part in movement of water in a plant. The high specific heat of water is also
due to hydrogen bonding, and is important in modulating the body temperature of
living things, as they are composed primarily of water. Hydrogen bonding also
results in the characteristic of ice to float, surface tension to exist at the surface of
bodies of water, the wetting characteristic of water, the structure of ice, and
evaporative cooling.