What is the name of the 10th planet in our solar system?

Well....Not so fast! There IS no 10th planet that has yet been convincingly discovered, so the International Astronomical Union has not provided a name for it.

You don't name an astronomical body because you THINK it is there. You have to have firm evidence and an orbit for the body, which means that you have to be able to photograph or 'image' it to compute a unique orbit for it. Although there is some recent evidence that there might be a large object beyond the orbit of Pluto, it hasn't been detected, and so it cannot be named yet.