This Pokémon exudes a weak electrical charge from all over its body that makes it take on a slight glow in darkness. Raichu plants its tail in the ground to discharge electricity. It can loose 100,000-volt bursts of electricity, instantly downing foes several times its size. When its electricity builds, its muscles are stimulated, and it becomes more aggressive than usual.
Pokédex entry #26
raichu in Pokémon GO
It's possible to hatch raichu from an egg?
No, raichu can't be hatched.
Which are raichu’s strengths and weaknesses?
raichu is a electric type Pokémon. electric type pokémons are strong against water, flying pokémons but weak against electric, grass, dragon pokémons. They are not affected by ground type pokémons.