Drawing Lewis Structures

[Selena Yu 1H]

Is there ever an exception where you won't choose the atom with the lowest ionization energy as the central atom?

[Claire Lo 3C]

Hydrogen in some cases has lower ionization energy than other atoms. But it's almost never used as the central atom, except if the molecule is H2.

[Letty Liu 2C]

Hydrogen can never be a central atom.

[Bradley Whitworth 4B]

Only hydrogen. There will be cases though when maybe there are a few of the least electronegative ions that aren't hydrogen and they go in the center in different arrangements depending on how many there are. In the case of a fatty acid there are usually a bunch of carbons which in that case all go in a straight line in the center. In other cases like benzene a ring is formed so it differs.

[Nicholas_Gladkov_2J]

Is there ever an exception where you won't choose the atom with the lowest ionization energy as the central atom?

I believe that unless there's only two atoms in the molecule (no central atom), or there's a molecule that doesn't really have any central atom (Bradly mentioned a fatty acid), the atom with the lowest ionization energy will be the central atom.
Hydrogen can only make one bond, which is why it can't be central.

[Viviana Velasquez]

Hydrogen is an exception. It will never be the central atom.

[Arianna Perea 3H]

If you leave a lone pair instead of making it a bond, would it be considered wrong?

[Pablo 1K]

If you leave a lone pair instead of making it a bond, would it be considered wrong?

It depends on the structure as a whole and the overall charge. Try to make bonds but keeping ion mind the overall charge.

[RobertXu_2J]

Hydrogen is never used as the central atom.