Very Important Topics:

Chapter Name Percentage

Oscillations And Waves 10%

Rotational Motion 8%

Electrostatics 8%

Atoms And Nuclei 8%

Current Electricity 7%

Laws of Motion 6%

Magnetic effect of Current and Magnetism 6%

Important Topics:

Kinematics 6%

Thermodynamics 6%

Work Energy Power 5%

Optics 5%

Electronic Devices 5%

Properties Of Solids And Liquids 4%

Electromagnetic Waves 4%

Average Topics:

Electromagnetic Induction 3%

Alternating Current 2%

Physics And Measurement 2%

Dual Nature Of Matter And Radiation 2%

Communication Systems 2%

Gravitation 1%

Kinetic Theory of Gases 0%

Mathematics:

Very Important:

Integrals 9%

Probability 7%

Three Dimensional Geometry 7%

Trigonometry 7%

Vector Algebra 7%

Conic Sections 7%

Straight Lines 6%

Sets, Relations and Functions 5%

Matrices And Determinants 5%

Important:

Limits And Continuity 5%

Quadratic Equations 5%

Derivatives 5%

Permutation and Combination 4%

Complex Numbers 4%

Circles 3%

Binomial Theorem 3%

Sequences and Series 3%

Differential Equations 3%

Average Important :

Inverse Trigonometry 2%

Heights and Distances 1%

Application of Derivatives 1%

Statistics 1%

Mathematical Induction 1%

Mathematical Reasoning 0%

Application Of Integrals 0%

Chemistry:

Very Important:

Organic Compounds Containing Oxygen 10%

Equilibrium 8%

Chemical Kinetics 7%

Transition Elements (d and f block) 6%

s-block Elements 6%

Chemical Bonding And Molecular Structure 6%

Some Basic Principles Of Organic Chemistry 6%

p-block Elements 5%

Coordination Compounds 4%

Chemical Thermodynamics 4%

Important:

Organic Compounds Containing Nitrogen 4%

Redox Reactions 3%

Biomolecules 3%

Electrochemistry 2%

Atomic Structure 2%

Polymers 2%

Solutions 2%

Solid State 2%

Some Basic Concepts In Chemistry 2%

Classification Of Elements And Periodicity In Properties 2%

Average Important:

States Of Matter 2%

Hydrogen 2%

Hydrocarbons 2%

General Principles And Processes Of Isolation Of Metals 2%

Organic Compounds Containing Halogens 2%

Surface Chemistry 1%

Purification Characterization Organic Compounds 1%

Chemistry In Everyday Life 1%

Principles Related To Practical Chemistry 1%

Environmental Chemistry 0%

No one can predict the exact difficulty level of JEE Mains.

Rather than focusing on the difficulty level of the paper you must prepare yourself for the top expected level. You know they will not ask questions of level JEE adv. in JEE Mains so, better stop thinking this type of vague things.

Try to solve previous year questions and expect the toughest questions in these papers to be the part of the JEE Mains 2018.

All the very best and good luck.