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Atomic And Ionic Radius

C h e m g u i d e – q u e s t i o n s

ATOMIC AND IONIC RADIUS

1. A data book gives two different values for the radius of an oxygen atom . One is the covalent radius

(0.074 nm), and the other is the van der Waals radius (0.140 nm). Explain with the help of

diagrams how the two different values arise, and why the covalent radius is smaller than the van der

Waals radius.

2. The same data book gives the metallic radii of the Group 1 metals as follows:

metallic radius (nm)

0.152

0.186

0.231

0.244

0.262

Explain why the radius increases as you go down the group.

3. Atomic radius tends to fall as you go across a period, provided you ignore the noble gas at the end

of it.

a) Why is it necessary to ignore the noble gas at the end of the period if you are making this

generalisation?

b) Explain why the atomic radius falls as you go from sodium to chlorine in Period 3.

4. Across the first row of the d-block elements from Sc to Zn, there is a small fall in atomic radius

from Sc through Ti to V, but then the values fluctuate within the range 0.124 to 0.133 across the rest

of the series. Explain why the atomic radius stays reasonably constant across the d-block elements.

5. The bar chart shows the relative radii of the ions of the elements in Period 3.

Na+

Mg2+

Al3+

P3-

S2-

Cl-

a) The ions Na

, Mg

and Al

are said to be isoelectronic. Explain what that means, and state the

electronic structures of these three ions. (Simple notation like 2,8,4 will be fine.)

Atomic And Ionic Radius