And so, in the lake of an acid mine or the ocean of a cell, every ( \text{SO}_4^{2-} ) ion sits quietly, a perfect tetrahedral gem, stable and unbothered—because it knew how to count its regions and share its charge.
Sulfur looked at his six valence electrons and frowned. "I only have six to give, but I need to satisfy four guests." so4 2 electron geometry and molecular geometry
Sulfur made a decision. He would use his d-orbital expansion. He promoted one of his 3s electrons to a higher energy level, creating six unpaired electrons. Then, he borrowed two extra electrons from the universe (giving the ion its ( 2- ) charge). Now, with eight electrons to allocate, he invited the four Oxygens to bond. And so, in the lake of an acid
"Since all four electron regions contain atoms," declared the Molecular Geometry, "your visible shape is... ." He would use his d-orbital expansion
Deep in the valley of the Periodic Table lived a large, charismatic atom named Sulfur. Sulfur was unique. Unlike his neighbor, the rigid Carbon, Sulfur had an expanded wardrobe—empty d-orbitals that allowed him to dress up in more than eight electrons. Today, Sulfur faced a dilemma. He had four Oxygen atoms asking for his attention. Each Oxygen needed two electrons to complete its own valence shell.
Thus, the looked exactly at the atoms. Four Oxygen atoms, all identical, all tugging equally at Sulfur.
He formed four double bonds (S=O). But to the Electron Geometry, those double bonds count as just of electron density each. So, looking at the electron clouds only: Sulfur had four regions of high electron density pushing away from him.