There is no such Marks Distribution For JEE Mains but a trend can give you an Idea which are being prepared by Top Coaching Institutes of IIT-JEE.

IN 2019 JEE Mains trend shows that-

PHYSICS:- Physics, Heat & Thermodynamics, Optics, Current Electricity & Magnetism holds around 76 Marks Out of 120.

CHEMISTRY:- Transition Element, Coordinate Geometry , Periodicity, Thermodynamics, Gaseous State, Atomic Structure, Chemical Bonding, Solid State & Surface Chemistry, Chemistry in Everyday life, Biomolecules, Polymers, Aromatic Compounds holds around 80 Marks out of 120 .

MATHS:- vector ,3D, Statistics ,Probability, Matrices, Determinants, Complex Number, Quadratic Equation, Integral Calculus, Limits-Continuity & Differentiability  , and Coordinate Geometry Together makes 84 Marks of total 120 marks.

SO IF U EXCELLED IN THESE , LEAVING REST you can still score 66% Marks in Competitive Exam like Jee with >1Million Aspirants. With 198/300 U can get top 3 NITs (Technical Institutes) of Country for your B.Tech Degree & take Good Placements from Companies like Amazon, Google and Oracle with whopping 1M Rupees Per Annum as Salary.

GO & GRAB IT!

Dear Aspirant
There is no such weightage of jee mains .You have to focus on all topics equally.But you can point out the chapters from which question occurs generally.For exampler From 11 th class Mechanics dominates the question paper .so you should practice lot for this particular topics .You must analyse the previous year question paper and solve them in least time.
I'm chemistry you should focus on all three Physical, inorganic and organic.
Thanks
All the very best

Hey!There.
It is not possible to mention topicwise weightage of every topic of each subjects..For detailed analysis refer to below mentioned link:
https://www.google.com/url?sa=t&source=web&rct=j&url=https://engineering.careers360.com/articles/jee-main-syllabus-weightage/amp&ved=2ahUKEwj2qM6GlczmAhWt7nMBHRBnDosQFjADegQIBhAF&usg=AOvVaw39V96qKf4tM9aqg7N06nT2&ampcf=1

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