Question

Is `C_2^-` paramagnetic or diamagnetic?

Answer 1

We have 13 electrons -- six from each carbon atom plus one more for the negative charge. With an odd number at least one is unpaired. Thus `"C"_2^-` is paramagnetic.

Explanation:

As you likely know, paramagnetism comes from unpaired electrons aligning their spin with a magnetic field. For typical molecular species this is the prediminant magnetic interaction -- if we can find an unpaired electron.