How do you draw the Dot and Cross diagram of the Sulphate Ion?

I believe S has an expanded octet and forms 6 bonds to the O atoms (2 are double and two are single).

When you draw this out you have two of the Oxygen atoms with only 7 electrons in their outer shells. At this point add an electron into each outer-shell to make it up to 8. These two extra electrons give the ion its overall charge of 2-.

You must put square-brackets around the whole diagram and show the charge in the top-right corner.

My tip is to use dots for the O electrons and add "filled-in" dots to show they came from elsewhere.