Pichu evolves from pikachu than pikachu evolves from raichu.
A Pikachu evolves from a Pichu.
It evolves into Pikachu with Happiness. Pikachu then evolves into Raichu via Thunderstone
Pikachu evolves into Raichu. To evolve it, you have to use a Thunderstone on it.
Pikachu evolves into a Raichu.
pikachu evolves into raichu with a thunder stone!
Pikachu evolves into Raichu when given a Thunderstone.
Pikachu evolves into Raichu with a ThunderStone.
Pikachu evolves with a thunder stone.
Well... I should probably tell you which Pokemon it generally evolves. It evolves Eevee to Jolteon and Pikachu to Raichu.
Raichu never evolves. Unless you meant Pikachu, which evolves into Raichu. Or Pichu, who isn't in Leafgreen but evolves into Pikachu, then Raichu.
pikachu evolves via thunderstone
You need a thunderstone for Pikachu to evolve into Raichu.