Question

Is there any formula to calculate bond lenght of two elements

Answer 1

if it is a covalent bond, the formula is

r(a) + r(b) - 0.09(∆E) (if radius is in picometer)
r(a) + r(b) - 9(∆E) (if radius is in angstrom)

r(a) = radius of first element.
r(b) = radius of second element.
(∆) = difference between their electronegativities