Why is it wrong to draw the Lewis structure of a molecule's atoms and then figure out the Lewis structure of that molecule

When drawing for example the Lewis structure of nitrate ion (NO3)^-1 whould it be wrong to draw nitrogen and oxygen separately and then try to figure out the structure of the ion? In that case does the nitrogen give one of its electrons to the oxygen? cause a nitrogen atom does have a lone pair of electons but in the nitrate ion they are gone.

• Nitrogen atom has a lone pair and three free electrons around it. If you surround the nitrogen atom with three oxygen atoms, three electrons of the nitrogen atom can make a bond with an electron belonging to the oxygen atoms. This would give to the nitrogen atom a structure respecting the octet rule. But not the oxygen atoms. They do not respect this octet rule, even with adding a supplementary electron to make $\ce{NO3^-}$. The only way to give oxygen an octet is to break the lone pair, as you did previously.. Jun 5 at 19:33