What is the number of unpaired electrons in Fe 2+? Specifically, how can I find out the number of unpaired electrons in any ion?
First draw the electronic configuration for Iron.

Now since we are given with Iron(II) we take out two electrons from the outermost orbit so as to give the iron a +2 charge.



As evident from the configuration, in total there are 4 unpaired electrons.

Using the same logic you can count the number of unpaired electrons for any ion.