Put a glove on and kind of rub it a bit and see if you can see it breathing. If you can't tell it probably is no longer alive or was born dead. Usually once kittens are born they start walking and go and nurse off of the mom. If it is alive put it right back up to the moms milk and don't touch it there after for a few weeks, til they are bigger. Some times, if it is the moms first litter of kittens they usually don't make it at all. At least that is what we have seen. And the next batches do.