Question

How to calculate atomic radii of triatomic molecules?

Answer 1

ANSWER⤵️

Atomic radius is the distance from the centre of the nucleus to the point  where the electron density is effectively zero.

a.Homonuclear diatomic molecules

In case of homonuclear diatomic molecules of A2 type (e.g. F2, Cl2, Br2, I2 ... etc.) the bond length, d(A-A) is given by

 

d(A - A) =   r(A) + r(A)

d(A - A) =   2  r(A)

r(A) =  d(A-A) / 2

The above equation shows that in the case of homonuclear diatomic molecule of A2 type, the covalent radius of an atom A, r(A) is equal to one half of the inter- nuclear distance, d(A-A). Therefore, the covalent radius of an atom in ahomonuclear diatomic molecule can be obtained by dividing the internuclear distance by two.

 

Example

1. Cl2 molecule

The value of Cl-Cl bond distance as found experimentally is 1.98. Thus

r(Cl)= d(Cl- Cl) /  2 = 1.98/2 = 0.99.