The four Oxygens stood at the corners of a tetrahedron, repelling each other equally. The molecule was symmetric, stable, and perfectly non-polar in its charge distribution, despite carrying a net negative charge.
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. so4 2 electron geometry and molecular geometry