 Typically what one does when they do this is think something like this. That's not right because the angle from here to here is 90 degrees. The angle from here to here is 180. What we know is that there is a theory called valence shell electron repulsion theory that is the electrons are going to make a cloud and that cloud is going to repel other electrons and push them as far apart as possible. So you see these are 90 degrees. They're a lot closer. So we need to move our toothpicks so that they're about 109 degrees apart so that the distance from here to here is 109, from here to here is 109, from here to here is 109, and here is 109. So you need to practice that and try to envision what that's going to look like. So that's our tetrahedron. I want to help you make the first model. First let's look at methane, CH4. You know if you have a carbon you need to draw the Lewis structure. That would give you four electrons around the carbon and four from the hydrogen. And then we would need to attach a hydrogen to each one of these carbons. So here we have our carbon, we put a hydrogen on each one of these, and now we have a tetrahedron. So your task is to make the Lewis structure for each atom, connect it to the other atoms to make the molecule, sketch the geometry, and then discuss the angles and the hybridization.