What makes up the remaining 3 percent of earth?

Answer 1

The question implies a list of elements or compounds, or mixtures or some combination which account for 97%. With no information about that 97% it is not possible to provide an answer.

Answer 2

The remaining 3% of Earth is composed of other gases like argon, neon, helium, and methane, as well as aerosols and trace amounts of pollutants. These components play a minor role in the atmosphere but can still have significant impacts on climate and air quality.