Since Electrum's seeds are made up of
(AFAIK 2048) Dictionary words it would be possible to brute-force it, however it would probably take a while (and may not be worth it for a small amount of Bitcoin).
Do you remember the order of the 7 words that you know? If so, that would likely make it significantly faster (It would have to check 2048
5 combinations rather than 2048
12).