CHEMISTRY 3.4
Name:
WORKSHEET FOUR
RADII OF ATOMS AND IONS
1.
(a)
Determine the atomic radius of the four elements shown below by using the
information given in the chart.
Metallic sodium
Phosphorus (P4)
Chlorine (Cl2)
Iodine (I2)
Element
(not to
scale)
1. 12 x10 - 9m
2. 2 x10-10 m
2. 0 x10-10 m
2. 7 x10-10 m
Atomic
radius
(b)
(c)
(d)
Sodium, silicon and chlorine are all in the same row of the Periodic table.
(i)
Describe the trend in atomic radii across a period.
(ii)
Explain the reasons for this trend.
Chlorine and iodine are in the same group of the Periodic table.
(i)
Describe the trend in atomic radii down a group.
(ii)
Explain the reasons for this trend.
Explain why it is difficult to measure the atomic radii of the “Inert Gas” elements.
2.
The atomic and ionic radii of several elements are given below in pm (1 pm = 1x10-12 m).
Element
Li / Li+
Be /Be2+
N / N3-
O / O2-
F / F-
Na /Na+
K / K+
Atomic radii
152
112
75
73
72
186
227
Ionic radii
90
59
132
124
117
116
152
Using the information in the table, answer the following questions.
3.
(a)
For an element, its positive ion is
than its neutral atom.
(b)
For an element, its negative ion is
than its neutral atom.
(c)
(d)
Within a group, the size of the ions with the same charge
down the group.
Explain your answer to (a).
(e)
Explain your answer to (b).
(f)
The following are isoelectronic: P3-, S2-, Cl-, Ar, K+, Ca2+. Compare and discuss the
expected values of their radii.
as you go
In each of the following groups of atoms and ions, circle the one with the smallest radius.
(a)
B, Al, Ga
(b)
Cs, Cs+
(c)
P3-, S2-, Cl-
(d)
Li+, N3-, O2-
(e)
F, Cl, Br, I.
(f)
S, S2-
(g)
Cl, Cl-
(h)
Mg, Mg2+
(i)
Na+, Mg2+, Al3+