molecular shape-seesaw

[204929947]

How do you know when it is a seesaw shape? I get it confused with the tetrahedral shape :(

[Cindy Nguyen 1L]

6 regions of electron density = 5 bonded atoms + 1 lone pair. ex. SF4. Tetrahedral has 4 regions of electron density.

[Yeo Bin Yook 1K]

For molecules like sulfur tetrachloride the reason why its shape is seesaw is primarily because the electrons want to be as far from each other as possible. If not it would look like a trigonal bypyrimidial but the lone pair would rather be at 120 degrees than 90.