Is this a good team on pokemon black and white?

Well if you're talking about Nintendo's VGC, you can only use 5th gen pokemon and they're double battles. However if it's any other tournament that is single battle it looks pretty good, though if you're using charizard, I would find a rapid spinner for your team, as stealth rocks could wipe out your charizard easily, especially if it's a belly drum build. Either that or replace it for another physical sweeper; Lucario, Garchomp, Scizor, and Excadrill are each very good contenders, especially for a sandstorm team like yours. Just make sure you actually EV train them and get good IVs for them or you'll get wiped out. If you're having difficulty deciding, or thinking of a different team, test them out on this online emulator people use to test out their teams before actually making them, I'll post the link below. The site also shows good builds for each pokemon that you may consider. Hope this helps. :)