Calculate the theoretical value of Bond Length of $\text{H-F}$ . If  ${\text{r}}_{\text{H}}\text{, }{\text{r}}_{\text{F}}$ are $\text{0.37}\mathrm{\AA }$ and $\text{0.72}\mathrm{\AA }$ . ${\text{X}}_{\text{H}}=\text{2.1}$ & ${\text{X}}_{\text{F}}=\text{4}$ are given.

Arrange as directed:

$\mathrm{S} \left(16\right), \mathrm{O} \left(8\right), \mathrm{Te} \left(52\right), \mathrm{Se} \left(34\right)$ belonging to Group 16 of the long periodic table according to increasing order of electronegativity. 

(The atomic numbers have been given within first brackets after the symbols of the elements)