Though it was speculated that the syllabus would change for JEE Mains 2021, only the exam pattern changed and the syllabus remained the same. You can check that at: https://engineering.careers360.com/articles/jee-main-syllabus#JEE-Main-Syllabus-2021-Physics-Chemistry-Mathematics There is no negative marking for few set of questions. This means,  there will be no negative marking in the 15 alternative questions. The candidates have to attempt 75 questions out of 90  or 25 out of questions 30 in each section of Chemistry, Physics and Mathematics.  But the previous questions papers will have a slightly different exam pattern.  But to give you an idea,

Mathematics:

Sets, relations and functions

Complex numbers and quadratic equations

Matrices and determinants

Permutations and combinations

Mathematical induction

Binomial theorem and its simple applications

Sequences and series

Limit, continuity and differentiability

Integral calculus

Differential equations

Coordinate geometry

Three dimensional geometry

Vector algebra

Statistics and probability

Trigonometry

Mathematical reasoning

Communication systems

Physics:

Physics and measurements

Kinematics

Laws of motion

Work, energy and power

Rotational motion

Gravitation

Properties of solids and liquids

Thermodynamics

Kinetic theory of gases

Oscillations and waves

Electrostatics

Current electricity

Magnetic effects of current and magnetism

Electromagnetic induction and alternating currents

Optics

Dual nature of matter and radiation

Atoms and nuclei

Electronic devices

Chemistry:

Some basic concepts of chemistry

States of matter

Atomic structure

Chemical bonding and molecular structure

Chemical thermodynamics

Solutions

Equilibrium

Redox reactions and electrochemistry

Chemical kinetics

Surface chemistry

Classification of elements and periodicity in properties

General principles and process of isolation of metals

Hydrogen

S - block elements - alkali and alkaline earth metal,

P - block elements, group 13, 14, 15, 16, 17, 18 elements,

D and f block elements

Coordination compounds , Environmental chemistry

Purification and characteristics of organic compounds, Some basic principles of organic chemistry

Hydrocarbons,

Organic compounds containing halogens, oxygen and nitrogen

Polymers, Biomolecules, Chemistry in everyday life,

Principles related to chemistry