The Van der Waals radius is defined as:

Half of the distance between the nuclei of two non-bonded identical atoms when they are just touching each other.

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Simple Understanding

• When atoms are not chemically bonded (no covalent/ionic bond), they still can come close due to weak intermolecular forces.
• The distance at this closest approach = Van der Waals distance
• So,
  Van der Waals radius = (Van der Waals distance) / 2

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Example

If two neon atoms (not bonded) are 3.2 Å apart:

• Van der Waals radius of neon = 3.2 / 2 = 1.6 Å

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Correct Order of Atomic Radii:

Van der Waals radius > Metallic radius > Covalent radius

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🔹 Why this order?

1. Covalent radius (smallest)
   • Atoms are strongly bonded
   • Nuclei pull shared electrons → atoms come closer
2. Metallic radius (middle)
   • Metal atoms are packed in a lattice
   • Bonding is weaker than covalent → atoms are slightly farther apart
3. Van der Waals radius (largest)
   • No bonding, only weak attraction
   • Atoms stay far apart

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🔹 Comparison Table

Radius Type	Condition	Smaller/Larger
Covalent radius	Bonded atoms	Smaller
Metallic radius	Metal lattice	Medium
Van der Waals	Non-bonded atoms	Largest

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