That's an Atom that is probably soldered to the motherboard. They aren't commonly sold at retail and even if they were, you would not be able to replace it. From the Wikipedia page on the flip chip BGA socket:
The processor is affixed to the motherboard by soldering the balls to the motherboard. This allows for a much thinner CPU/interface profile than a pin grid array socket arrangement, but the micro-FCBGA chip is not removable from the motherboard.
If you have 1GB RAM you can probably expand it to 2. That should gain some performance.
Even if you could, what o1die is also true.