The initial structure (Structure A) looks like this:
We started with 32 electrons. After using 8 for bonds, we have (32 - 8 = 24) electrons left (or 12 lone pairs). Oxygen atoms are greedy for electrons. To satisfy the octet rule, each oxygen needs 6 more electrons (3 lone pairs) around it. (4 \text oxygens \times 6 \text electrons = 24) electrons. Perfect. so4 lewis structure
.. .. :O: :O: | | ..:O--S--O:.. | | :O: :O: .. .. At first glance, every atom has an octet. Sulfur is surrounded by 4 single bonds, meaning it has 8 electrons around it. So why is this structure incomplete? The answer lies in . 2. The Problem of Formal Charge Formal charge is a bookkeeping tool that helps us identify the most stable, plausible Lewis structure. It does not represent a real charge, but rather the electron “ownership” difference between an atom in a molecule and a free atom. The initial structure (Structure A) looks like this:
Our goal is to distribute these 32 electrons as bonding pairs (lines) and lone pairs (dots) to satisfy the octet rule for as many atoms as possible. To satisfy the octet rule, each oxygen needs
Connect each oxygen to the sulfur with a single bond (a line representing 2 electrons). This uses up (4 \text bonds \times 2 \text electrons = 8) electrons.
Sulfur is less electronegative than oxygen. Therefore, sulfur is the central atom. The four oxygen atoms surround it in a tetrahedral arrangement (though we draw it in 2D with S in the middle and O’s at the four cardinal points).