the a-330-500 is a shortened version of the a-330-200. airbus didn´t want to call it -100, because that could trigger an image of less performance and less quality, so they opted for the -500.
this plane was basically developed as a replacement for ageing a-300/310s under pressure from lufthansa, hapag-lloyd and singapore so they could retire their fleets of a-300/310s.
at first, airbus wanted to use the a-330 fuselage but the wing of the a-300 so that it wouldn´t become too big and heavy. but that idea was let down, and so the a-330-500, which is not formally launched yet, would feature a shortened a-330 fuselage and a-330 wings.
because of this, the wide wingspan and the massive weight, lufthansa responded that this plane was unsuitable for its domestic and european network, on which it uses its fleet of a-300/310s.
at the moment, airbus has two different a-330-500 variants on its paper, one with a range of 8000km and one with even more range than the a-330-200, which actually is not surprising.
hope i could help you
If only pure sweetness was offered, why's this bitter taste left in my mouth.