Why might uranus and neptune have proportionally less elemental hydrogen in their atmosphere than their more massive companions, jupiter and saturn?

Idk if this helps but, Uranus' atmosphere has tons of hydrogen and other elements which is more likely to absorb colors at the red end of the spectrum and is more likely to reflect back blue-green light

sry if not helpful

Each names a given number of objects

True, the standard unit for volume is liters which can be represented by either a lower case "l" or a capital "l"