Monika, GATE is an entrance exam for admisison to Post Graduate courses in Engineering, Technology and relevant Science courses. While JEE is the entrance examination for admission to Undergraduate courses like B.Tech/B.Arch. So there is a vast difference in the syllabus. You can check the complete syllabus for Chemistry in our article: https://engineering.careers360.com/articles/gate-syllabus . But to give you the gist,

Under Physical Chemistry topics like Structure, Equilibrium, Kinetics and Surfaces and Interfaces.

Under Inorganic Chemistry, topics like Main group Elements, Transition elements, Lanthanides and Actinides, Organometallics, Radioactivity, Bioinorganic Chemistry, Solids, Instrumental Methods of Analysis.

Under Organic Chemistry, topics like Sterochemistry, Reaction Mechanisms, Organic Synthesis, Pericyclic Reactions and Photochemistry, Heterocyclic Compounds, Biomolecules and Spectroscopy.