NO3-

[ALee_1J]

Why does NO₃^- have nitrogen as the center atom? I know that center atoms are the ones with lowest ionization energy but doesn't oxygen have a lower ionization energy than nitrogen due to its lone pair and electron-electron repulsion?

[JonathanSung_2G]

I think that when drawing Lewis structures for molecules, we should factor in symmetry; a lot of times we want to draw atoms that are symmetrical on all sides. Also, if oxygen is the center atom, then that means that the other oxygens and nitrogens will have to bond to it, but we don't typically see oxygen bonding to oxygen unless its O2. Usually, it's the atom with the lowest ionization that is the center atom, but it's possible that exceptions may exist.

[rachelhchem1I]

In addition to symmetry, I think you should just go with the general trends of the periodic table rather than looking at specific values. Because in terms of ionization energy trends, N should be lower than O, but Oxygen is sort of an exception for this trend. I think this could be why N is still in the middle.

[SelenaDahabreh1D]

I think Nitrogen, in this case, would be an exception because while drawing Lewis structures, symmetry also plays a role in determining the shape.

[Jaden Ji 2K]

I think it is because the oxygens tend to bind to the nitrogen rather than each other like Jonathan said before me.