[JonathanEyoon]

How many unpaired electrons are there in an O^2- ion?

[Alpha-Omega]

I am afraid I will have to make you work for this.  You can do it.  It is easy.  Just count. 

1.  Write out the electron configuration for oxygen.

2.  The you have to write out the electron configuration for the O^2- ion.

3.  Keep in mind that when you form the O^2- ion you are adding 2 electrons to the neutral oxygen electron configuration.  HINT:  What happens to the 2p shell.   

4.  The keep in mind that this is going to be isoelectronic (same number of electrons) with a certain nobel gas.  So for the O^2- ion there is a shorthand notation you can write for its electronic configuration. And what is special about the electron configuration for a nobel gas?   

5.  So how many unpaired electrons do you see?