# Is SO3 an ion or a molecule?

Earlier I thought that $\ce{SO3^{2-}}$ (sulfite) is an ion with -2 charge but today I read on internet $\ce{SO3}$ (sulfur trioxide) is a molecule with no charge. How can this be possible? Please explain knowing that I am only a student of 10th standard (use normal chemistry concepts as far as possible).

• Search in Google for their molecular structures. You'll understand the difference. – Wrichik Basu May 16 '17 at 18:50
• For one thing, $\ce{SO3^{2-}}$ has two extra electrons, so it's an ion. $\ce{SO3}$ is a neutral molecule. There are a different number of electrons, so they're just different. – Zhe May 16 '17 at 18:57
• The key is that they actually have different molecular formulae and are thus different compounds. Remember that charge counts ;) – airhuff May 16 '17 at 18:58
• It's pretty hard to explain this to a 10th grader. Just wait for a while, 11th grade teaches you all about different types of bonds. :) – Pritt says Reinstate Monica May 17 '17 at 2:40

Resonance structures of $\ce{SO3^{2-}}$ ion:
• I don't think that is the structure of $\ce{SO3}$. The real structure has one double bond and 2 dative bonds. – Pritt says Reinstate Monica May 17 '17 at 2:38