In Gmail, when I view an individual email (like an ad from Kohl’s) and hold my tablet vertically, the entire screen shows the ad.  Problem is that I have to scroll both horizontally and vertically to see the whole ad.  Now if I turn my table to the horizontal position I would expect the screen to rotate and to be wide enough so that I would only have to scroll vertically to see the entire ad.  But that doesn’t happen.   The screen rotates OK, but then splits into two panes.  On the left is the list of email folders and on the right is the ad I wish to view which is now half the size that it was when I held the tablet horizontally.
Is there a way to get rid of the folder list and have the entire screen display only the ad?

Dick