The covalent radius of an element is considered to be one half of the covalent bond distance of a molecule where the atoms concerned are participating in single bonding. In other words, It may be defined as one-half of the distance between the centres of the nuclei of two similar atoms bonded by a single covalent bond. The covalent radius of an atom is the radius of an atom under the covalent bond with another atom(s) of a similar element. The covalent radius of an atom can be determined by measuring bond lengths between pairs of covalently-bonded atoms.
Covalent and van der Waals radius
Van Der Waals Radius
Van-der-Waals radii are determined from the contact distances between unbonded atoms in touching molecules or atoms.
- The covalent radius of the elements is shorter than its van der Waals radius.
- The formation of a covalent bond involves the overlapping of atomic orbitals.
- As a result of this, the internuclear distances between the covalently bonded atoms is less than the internuclear distances between the non-bonded atoms.
- The covalent radii vary with the type of bond between the atoms.
- The values of covalent radii may also differ between allotropes. For example, the covalent radius of carbon is 77pm in diamond and 71pm in graphite.
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