Yes indeed, they are a direct swap. Now as long as the said wheels have the original size tires that were used on the Ion, you’ll have no problems. Just make sure yours is a 4 lug and should be good to go.
Not sure which wheels you’re looking at. The double spoke X wheels? Or 5 spoke with the inset center? The second were the ones I had looked at. But had wanted to wait until I find them in better shape. Most I looked at had corrosion on the edges which is common for machined finish that’s clear coated.
Now the Ion wheels that don’t work on 4 lug Cobalts are the Redline wheels. Unless you do a 5 lug swap. Would be cool, but a bit of work and parts. It’s doable though.