Hello Aspirant,

Hope you are doing well.

Important topics to score 180 marks in JEE Mains April 2021 are:-

Mathematics:-

• Coordinate Geometry
• Limits, Continuity and Differentiability
• Integral Calculus
• Complex numbers and Quadratic Equation
• Matrices and Determinants
• Statistics and Probability
• Three Dimensional Geometry
• Vector Algebra

Physics:-

• Modern Physics
• Heat and Thermodynamics
• Optics
• Current Electricity
• Electrostatics
• Magnetics

Chemistry:-

• Transition Elements and Coordination Chemistry
• Periodic table and Representative Elements
• Thermodynamics And Gaseous State
• Atomic Structure
• Chemical Bonding
• Chemical And Ionic Equilibrium
• Solid State And Surface Chemistry
• Nuclear Chemistry And Environment

these topic score more marks

Some other topic with less weightage are:-

Mathematics:-

• Set, Relation and function
• Permutation and Combinations
• Binomial Theorem and its application.
• Sequences and series
• Trigonometry
• Mathematical Reasoning
• Differential Reasoning
• Statics and Dynamics
• Differential Calculus

Chemistry:-

• Mole Concept
• Redox Reaction
• Electro Chemistry
• Chemical Kinetics
• Solution and Colligative Properties
• General Organic Chemistry
• Stereochemistry
• Hydrocarbon
• Alkyl Halides
• Carboxylic Acid and their Derivatives
• Carbohydrates amino acid and polymers
• Aromatic Compands

Physics:-

• Unit, Dimension and Vector
• Kinematics
• Law of motion
• Work, Power and Energy
• Centre of mass
• Rotation
• Gravitation

Firstly, you have learn the high weightage topic then you have cover low weightage topic.

For more information I'll providing you a link:-

https://engineering.careers360.com/articles/jee-main-syllabus-weightage

Feel free to ask any query.

All the best for your bright future ahead.