Question

Why MnF3 has three different Mn-F bond length?​

Answer 1

$\huge\underline\mathfrak\blue{Answer}$

The length of the bond is determined by the number of bonded electrons (the bond order). The higher the bond order, the stronger the pull between the two atoms and the shorter the bond length. Generally, the length of the bond between two atoms is approximately the sum of the covalent radii of the two atoms.1