Ok so i bought some 4000 series logic gate chips the other day

I connected a circuit up with a 4081 series chip (AND Gate):

http://upload.wikimedia.org/wikipedia/en/c/c5/AND_Pinout.png

I had power going in to the chip at point 14 and out again at 7, then i had only one other connection, at point 3 which was connected via an LED to the negative terminal of the battery again, so why did the LED light up?

is my chip broken?

because a1 and b1 has to be logic "1"

edit:
you asked why it DID light, i thought it said didn't.
revised answer is that all unused inputs/ outputs MUST be connected either to Vdd or Vss unless they are being used. in your case pins 4, 5, 6, 8, 9, 10, 11, 12, 13 must be connected to Vss.

also make sure the led is connected properly, cathode to Vss.
apply a high to pins 1 and 2 to light the led.

also you do understand that Vss is "ground" or negative, right ?

Basically what he said. We're talking logic here. When you don't connect to either source or sink, you leave it floating. Better to give it a firm logic 1 or logic 0.