Answers to 5-3 Apply: Two Trendy Elements
1. Sodium and Chlorine are in the same period but sodium has a much bigger
radius than Chlorine because it has a smaller nuclear charge (number of
protons) pulling on the electrons.
2. Na would have a +1 charge because it will lose the only electron it has in the
3rd energy level. By doing this it will obtain the noble gas configuration of Ne.
Chlorine is only one electron shy of having a completely filled sublevel and
therefore will take an electron to form a -1 charge thus obtaining the noble
gas configuration equal to Ar.
3. The I.E. for sodium is much lower than the I.E. for chlorine because it is easier
to remove an electron from a sublevel when there are fewer electrons in the
outer level.
4. Chlorine has a much higher electron affinity than sodium because chlorine is
only one electron away from forming noble gas electron configuration.
5. (can’t draw on the computer) For Na, remove the electron from the outer
level representing just the core electrons. For Cl, add an electron to the outer
layer and make the third level a little bit bigger.
6. The Na ion is now smaller than the Cl ion because when metals lose electrons
their size gets smaller and when non-metals gain electrons their size gets
bigger.
5-3 Practice Problems
1. a. Cl 6. Rubidium atom
b. Cl
7. Bromine atom
2. a. Se
b. S 8. Lithium ion
3. a. La 9. Tellurium ion
b. La
10. a. Al
4. a. Cr b. P
b. Cr
5. a. N
b. As
