installing 10.6 to a external hard drive on a 10.7 computer

Hi, I have a late 2006 imac and a late 2006 macbook without a superdrive. My macbook had a 60 gb hard drive and I got a 500 gb hard drive for it, I formatted the hard drive with my imac and put a snow leopard disk inside it to install it to the macbook. The imac is running lion so when i put the disk in it and it wouldnt work. I want to install snow leopard to the blank disk in the macbook via firewire so it should let me install it. Could i download lion off the app store on my imac and select the disk to install it on?

Thanks,

Ted.