Welcome to Chem Zipper.com......: Covalent radius:

## Sunday, August 15, 2021

Covalent radius: It is defined as one half of the distance between the nuclei (inter nuclear distance) of two covalently bonded like atoms in a homo nuclear diatomic molecule is called the covalent radius of that.

(A) For Homo atomic Molecules: The covalent radius (rA) of atom A in a molecule A2 may be given as:

The distance between nuclei of two single covalently bonded atoms in homo diatomic molecules is equal to the sum of covalent radii of both the atoms.

Illustrative example (1): A given compound A2 whose total dA-A is 1.4 A0. The atomic (covalent) radius of an atom is.

Solution:  We known that

(B) For Heteroatomic Molecules: In a hetero diatomic molecules AB where the electro negativity of atoms A and B are different, the experimental values of inter nuclear distance dA-B is less than the theoretical value (rA +rB).

(1) Stevenson & Schoemaker Equation (1941):

Covalent radius of heterogeneous molecule like A-B etc determine by Stevenson & Schromaker Equation, if atoms are formed different type of covalent bond i.e. on atom is more electronegative than the other combined atom. Then the covalent radius is calculated by the relation given by Stevenson & Schoemaker, given as:

For a diatomic Hetero molecule:

Bond Length (lA-B) = r+ rB- 0.09(XA-XB)

Where XA= Electronegativity of more electronegative atom

Where XB= Electronegativity of less electronegative atom

### (5) The C–C single bond length is 1.54 Angstroms and that of Cl–Cl is 1.98 Angstroms. If the electronegativity of Cl and C are 3.0 and 2.5 respectively, the C–Cl bond-length will be equal to ?

(2) Puling equation: If the electro negativities of the two atoms A and B are XA and XB   respectively then

Bond Length (dA-B) =( rA +rB)-(C1XA-C2XB)

Where C1 and C2 are the Stevenson’s coefficients for atoms A and B respectively

Related Questions:

### (15) What are the increasing order of molar conductivity of first group elements in water ? 