Chemistry Homework
Notes
08.30.13 Read pp. 158-165, problems pp. 165 #1-5, 10
1. Explain why the noble gases tend not to react.
Noble gases tend not to react because they have a full
valence (outer) energy level of electrons. (pp. 158-159.)
2. Where are the valence electrons located in an
atom?
The valence electrons are located in the outer (farthest
from the nucleus) energy level. (p. 160 & Figure 3.)
3. How does a cation differ from an anion?
Cations are positively charged ions and anions are
negatively charged ions. A cation is formed when an
atom loses one or more electrons. An anion is formed
when an atom gains one or more electrons. (p. 161 &
Figure 4.)
4. State the octet rule.
The octet rule states that atoms tend to gain or lose
electrons to form the same electron configuration as a
noble gas. (p. 159, 161.)
5. Why do the properties of an ion differ from
those of its parent atom?
The properties of an ion are different from the
properties of the parent atom because the ion has either
gained or lost electrons to become an ion. The ion has a
different number of electrons and different electron
configuration than the parent atom. Because electrons
determine chemical properties, changing the electrons
changes the properties of the substance. (p. 162.)
10. How could each of the following atoms react to
achieve a noble gas configuration?
A. iodine – This is a halogen in group 17. It has 7 valence
electrons and will gain 1 to form a stable ion.
B. strontium – This is a alkaline earth metal in group 2. It
has 2 valence electrons. It will lose 2 electrons to form a
stable ion.
C. Nitrogen – Group 15 non-metal. It has 5 v.e. It will gain 3
to form a stable ion.
D. Krypton – Noble gas. No reaction.