CP Chemistry
WS 2.3 Periodic Trends Key
Your graphs should look similar to the first two that you see below.
1.
2.
a) The radius typically decreases left to right across a period. According to Coloumb’s Law 𝐹 ∝
𝑄1𝑄2
as the magnitude of the charges increases the force of attraction from the protons in the
𝑑
nucleus increases; therefore, the radius decreases.
b) The radius increases from top to bottom as a result of increasing numbers of shielding electrons
(same thing as more energy levels) present. The shielding or screening electrons diminish the
𝑄1𝑄2
attraction of the protons for the valence electrons. According to Coloumb’s Law 𝐹 ∝
as the
𝑑
magnitude of the force of attraction decreases, the distance from the nucleus to the valence
electrons increases.
c) Ionization energy increases left to right across a period. As atomic radius decreases the force of
attraction from the nucleus increases; therefore, more energy required to remove electrons.
d) Ionization energy decreases from top to bottom of a group due to increased screening electrons.
𝑄1𝑄2
Valence e- are further from the nucleus and according to Coloumb’s Law 𝐹 ∝ 𝑑 as the
distance increases the force of attraction decreases; therefore, the ionization energy decreases.
3.
a) K because it has more energy levels
b) Ca because it has less protons pulling on it’s valence e- compared to Ni.
c) Ga because it has more energy levels
d) C because it has less protons pulling on it’s valence e- compared to O.
e) Br because it has more energy levels
f) Ba because it has more energy levels
g) Si because it has less protons pulling on it’s valence e- compared to S.
4. Moving left to right across a period the atomic radius decreases because there are more and more
protons pulling on the same outer energy level where the valence e- are. Moving down a group from
top to bottom the radius is increasing due to additional energy levels being added.
5. An increasing number of protons pull on the same outer energy level where the valence e- are, thus
causing the radius to decrease.
6. dfg
a) O
b) Be c) Ar d) Cu e) Ne f) V g) Ca h) Se
7. A positively charged cation is always smaller than the neutral atom that it came from, because metals
give away their valence e- to achieve a full outer energy level. Conversely, a negatively charged anion is
always larger than the atom it came from, because nonmetals gain electrons to have a full outer
energy level.
8. a) Na
b) S2c) Id) Al
9. Ionization energy is the energy required to remove a valence electron from an atom. The first
ionization energy is the energy required to remove the first valence e-, 2nd IE is energy to remove the
2nd valence e-, etc.
10. Increases across a period, because more and more protons pull on the same outer energy level
requiring more energy to remove successive electrons. Decreases down a group, because additional
energy levels place the valence e- further from the nucleus making them easier to remove.
11. a) Be, Mg, Sr
b) Cs, Ba, Bi
c) Na, Al, S
nd
12. (2 question # 10)
a) F
b) N
c) Mg
d) As
13. (question # 12) I’m sure this doesn’t need an explanation.