Effective overlapping will be shown by:

Draw the Lewis dot structure of the following:

${\mathrm{BF}}_3$

Draw the Lewis dot structure of the following:

${\left[\mathrm{B}(\mathrm{OH}{)}_4\right]}^{-}$

Draw the Lewis dot structure of the following:

${\mathrm{CO}}_2$

Draw the Lewis dot structure of the following:

$\mathrm{CO}$

Draw the Lewis dot structure of the following:

${\mathrm{B}}_2{\mathrm{H}}_6$