Whoa there! Depending on which model F2 he has, different lenses may fit.

This is an abbreviated description, but basically AI lenses index to the meter via a cutout in the rear mount of the lens. Pre-AI lenses use that little rabbit ear tab sticking out from the aperture ring. Most AI lenses also have the tab to allow them to be used on pre-AI cameras. A better description than I gave is at http://www.aiconversions.com/compatibilitytable.htm

Now, depending on the prism on his F2, he may or may not need the AI lens. If he has an earlier prism, such as the DP-1, an AI lens will work, but is not required. If he has a later prism, such as the DP-11, then an AI lens is necessary to allow metering with fully opened aperture.

When Nikon first came out with the AI lenses, they offered a conversion service that replace the rear section of the lens. Others, such as John White (the www.aiconversions.com site), would mill the existing ring and (at least in the one he did for me many years ago) add a sticker to allow the prism to show the aperture.

There is no harm in getting an AI lens for his F2, but be aware that non-AI lenses typically sell for a lot less than the same lens does if AI.