How old are the older chicks?... you don't want them pecking and picking on it ....I've never put chicks in with older ones til they are 3 or 4 months old and can take care of themselves and have places to get away from pecking or meanies...then you have to worry to about it getting enough feed...
Some have tried keeping an old fashion feather duster that you dust with in the brooder with the lone chick...and a mirror.....
Also maybe you can find a newly hatched chick close from someone.....