Study Guide: Periodic Table and Trends
Answers
1.
2.
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26.
D
B
C
A
A
D
C
B
C
A
Look this up online. Google search: periodic table groups
P = Group 15, Ca = Group 2 (alkaline earth metals), Kr = Group 18 (noble gases), Cs = Group 1
(alkali metals)
C
D
A
None of the answer choices are correct. The reason the positive ion is smaller than the neutral
atom is that when an atom loses its valence electrons, it loses its outside energy level, which
makes it smaller.
B
A
A
B
A
D
B
C
a) Cations are positive, so an atom has to lose an electron to become a cation. It becomes
smaller because it loses electrons (which means it loses its outside energy level as well).
b) Anions are negative, so they gain electrons. Electrons repel each other, so when an atom
gains another electron all of them push each other farther away and the atom becomes bigger
(this is called repulsion).
Ne, Se, Ge, Cd
PreAP Only
27. B (The more protons, the stronger the attraction between the protons and electrons. The
elements on the left have less attraction to their electrons than elements on the right, so they
have a lower ionization energy).
28. A (As you go up a group or family, there are less energy levels, and therefore there is stronger
attraction between a nucleus and the valence electrons. As you go down a group there are more
energy levels between a nucleus and the valence electrons. This is called shielding).
29. a) Ionic radius decreases (if the element is in group 1, then it will become a cation. Cations are
always smaller than the original neutral atom).
b) Ionization energy would be lower. (Elements on the right side of the periodic table have
higher ionization energies)
30. a) Atomic radius decreases across a period because there are more protons and electrons that are in
the same energy level. For instance, oxygen has 4 more protons and electrons than beryllium, but both
of these elements have energy level 2 as the highest energy level. The increase in + and – charge
(without an increase in distance between the electrons and nucleus) causes the electrons to draw closer
to the nucleus.
b) Atomic radius increases as you go down a group because of energy levels. Each time you go the next
element down a group, you are adding an energy level that is further away from the nucleus than the
last one. For instance, Lithium’s highest energy level is 2, and Sodium’s is 3; therefore, Sodium atoms
will be larger than Lithium atoms.