Answer
Jupiter’s atmosphere consists mainly of hydrogen $H_{2}$ (90 percent) and helium $He$ (9 percent).
while,
The Earth's atmosphere is composed of 21 percentage of oxygen $O_{2}$, 78 percentage of nitrogen $N_{2}$, 19 % other including $-\gt$ 0.9 percentage of argon, and 0.1 percentage some more gases like $CO_{2} , CH_{4}$ etc.
Work Step by Step
Jupiter is a huge planet and it can hold these hydrogen and helium with its gravity the gases dominated in the huge planet only because of its great gravity power. But the gravity of Earth is not strong that much , so atmosphere of Earth's has only free hydrogen , oxygen nitrogen abundantly and other gases that's the compositional difference.
