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arrange the following in order of increasing vanderwall's radius.F ,Cl ,O ,Ne ,N

arrange the following in order of increasing vanderwall's radius.F ,Cl ,O ,Ne ,N

Grade:11

3 Answers

Saurabh Kumar
askIITians Faculty 2400 Points
8 years ago
Our study of limonene showed that atoms do not approach each other closely when they are not bonded to each other. This suggests that atoms in different molecules cannot approach each other closely either and must occupy a well-defined molecular volume.

One way to measure molecular volumes is to study gas behavior over a range of temperatures. Real gases do not perfectly obey the ‘ideal’ gas law (PV = nRT), and deviations between ‘ideal’ and real behavior can give information about molecular volume.

It is also possible to measure intermolecular distances if a compound can be crystallized. One can pass X-rays through a crystalline solid and detect the X-rays when they emerge. The “bounce angle” gives information about atom positions, and one can use these data to calculate all kinds of interatomic distances.

Whatever its source, intermolecular distance data are interpreted by viewing the atoms as hard spheres. We assume that the spheres of neighboring nonbonded atoms just touch, so that the measured interatomic distance equals the sum of the atomic hard-sphere radii:
Hard-sphere radii are more commonly called van der Waals radii (or nonbonded radii). Reliable values cannot be given for these radii because they depend on the measuring technique and the molecule, but I have listed one useful set of radii in the following table.

van der Waals radii (in Å)

H C N O F P S Cl

These radii, like the bond radii discussed above, correlate with position in the Periodic Table:
As we go left to right within a row, van der Waals radius shrinks slightly (example: C > N > O > F)

As we go top to bottom within a column, van der Waals radius expands (example: F << Cl < Br < I)

Van der Waals radii can be used to study nonbonded (especially intermolecular) interactions. For example, one can compare an actual nonbonded distance with a predicted distance (the latter is obtained by summing van der Waals radii). If there is a “prediction gap”, that is, if the actual distance is substantially shorter than the predicted one, we might claim that some special force draws the atoms (molecules) together. We can also try to correlate the magnitude of this “prediction gap” with the strength of this attractive force.
SHANMUKESHWAR
461 Points
8 years ago
van der Waals radius shrinks slightly (example: C > N > O > F) …  van der Waals radius expands (example: F Cl
Anant Arya
24 Points
7 years ago
Ne
due to increase in effective nuclear charge from to right along the period radius decrease. Cl has an extra orbit. so it has largest radius.

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