The bond length decreases with bond multiplicity.

The bond lengths (in $\mathrm{pm})$ of $\mathrm{C}-\mathrm{C}\text{,} \mathrm{C}\equiv \mathrm{C}$ and $\mathrm{C}=\mathrm{C}$ are:

Find out the correct order of ionic character in the following molecules

$\left(\mathrm{i}\right) {\mathrm{SO}}_2$     $\left(\mathrm{ii}\right) {\mathrm{K}}_2\mathrm{O}$     $\left(\mathrm{iii}\right) {\mathrm{N}}_2$    $\left(\mathrm{iv}\right) \mathrm{LiF}$

How many ions of the following have a bond order of  $2.5 ?$ 

${\mathrm{N}}_2^{-};{\mathrm{NO}}^{-};{\mathrm{C}}_2^{-};{\mathrm{N}}_2^{+};{\mathrm{C}}_2^{2-};{\mathrm{CN}}^{+}$