The correct option is 2 and 3 only
Explanation
Atomic radius is not a fixed quantity because the electron cloud surrounding an atom does not have a sharp boundary. Consequently, atomic size is expressed in terms of operational definitions such as covalent radius, van der Waals radius, or metallic radius, depending on the bonding state of the atoms.
Statement-wise Analysis:
- Statement 1 is Incorrect.
The covalent radius is defined as one-half of the distance between the nuclei of two identical atoms bonded by a single covalent bond. The statement incorrectly defines it as the "total distance," which refers to the bond length (internuclear distance), not the radius. - Statement 2 is Correct.
The van der Waals radius represents the overall size of the atom, including its valence shell in a non-bonded context. It is defined as one-half of the internuclear distance between two identical atoms belonging to two adjacent molecules of an element in the solid state. - Statement 3 is Correct.
The formation of a covalent bond involves the overlap of atomic orbitals, which pulls the nuclei closer together. In contrast, van der Waals forces are weak attractive forces between non-bonded atoms where no orbital overlap occurs. Consequently, the van der Waals radius is always larger than the covalent radius for the same element.
Key Takeaway:
Covalent radius involves orbital overlap (shorter distance), whereas van der Waals radius represents the non-bonded distance of closest approach (longer distance). Therefore, $r_{vdw} > r_{metallic} > r_{covalent}$.