In reality, all four Sulfur-Oxygen bonds were —a perfect average between a single and a double bond (called a bond order of 1.5). The negative charge was spread evenly across all four Oxygens.
But the Oxygen atoms were democratic. They didn't like that only two got the "honor" of a double bond. So they did something magical: . so4 -2 lewis
Suddenly, a wise old floated by. "You have a secret power, Sulfur," it whispered. "You are in Period 3. You can expand your octet. Use your empty 3d orbitals ." In reality, all four Sulfur-Oxygen bonds were —a
"Let's bond!" said Sulfur. "I have six valence electrons of my own. You four each have six. Together, we can form a stable ring of eight." They didn't like that only two got the
But there was a problem. When Sulfur tried to share a single pair of electrons with each Oxygen (making four single bonds), he ran out of electrons. He was left with a miserable +4 formal charge, and each Oxygen had a -1 charge. The structure was unstable, like a table with three legs.