1st Gen yellow version Chansey

Kay, i threw like, A WHOLE BUNCH, of nourishment for the Chansey.
Then threw the safari ball multiple times.
Each time failed cause I missed hitting it or whatever.
Am I doing this wrong, or do I just have bad aim?
Any tips? :\

Throwing a rock at it will make it easier to catch, but more likely to make it run away.
Yeah, if you feed a Pokemon food, it'll stay for longer, but the Safari Balls will tend to miss.

You could either just throw a Safari Ball at it straight away and hope for the best (fingers crossed)
Or, if you just want a Pokedex entry, go to Cerulean cave and you'll find a Chansey there (provided you have beaten the Elite Four) but at a higher level than the ones at the Safari Zone.
I hope that helped.

the best is going to Cerulean cave and use a ultraball on Chansey, because in the safari zone its too hard!!