Is it normal that i can't defeat youngster joey's rattata in pkmn hg?

...
train your pokemon until its a few l vls above the rattata
I cant say I have ever had this problem

I forgot about leech seed.

You need to use fighting moves. They are good against normal types. I haven't played that game in a while, what level is his rattata? There's no shame in training and over levelling your Pokemon. Moves with status effects or Pokemon with contact effects should work too: Poison Sting, Wrap, static, burn, sleep, sleep powder, poison powder, paralyse powder, absorb, etc. Get your Pokemon 5 or more levels about his Pokemon. It you can afford permanent stat items, get some. Do you have more than one Pokemon in your party? Buy as many health items as you can.

Level up! Rare candies! Train! Learn more moves!

Oh! All yellow users!

use a FIGHTING type