That appears to be a normal juvenile Chaetodontoplus melanosoma... a very beautiful little specimen at that... there are a number of very closely related Chaetodontoplus species that share similar juvenile colorations (known as the melanosoma complex), of which C. melanosoma is the most white, although if you put your fish next to a black sheet of paper when you get it you'll probably see it as a whitish yellow... or a yellowish white... it will not be a clownfish white if you know what I mean...
Copps
First priority is getting that fish feeding fast and often. The amount of time these tiny angels could go without eating is much less than larger specimens... The advantage is that with small specimens like this if you acquire them in good shape they adapt to a captive diet much easier than larger individuals... large Chaetodontoplus are perhaps the biggest headache of all angels in getting them feeding... full size in the aquarium depends on many factors I've found... but probably in the 5-6" range...
Small angelfish are fish that require a QT session. Not for disease control, but for adapting to captivity. It's a place where they can be comfortable enough to start eating and build fat reserves. As small as that C. melanosoma juvi is, directly into a DT or into a QT with other fish, let alone another angel, is almost a death sentence.
I have a pair of small C. caeruleopunctatus that I picked up from the same place a week ago. Right now the only foods they are accepting are fresh cracked live clams. I would give that a try if you have troubles with getting the fish to eat. I would also considering removing one of the angels to the sump.