The uploaded PDF contains a comprehensive worksheet based on Chapter 2, Structure of Atom, for Class 11 Chemistry. This worksheet focuses on the discovery of sub-atomic particles, properties of electrons, protons and neutrons, cathode ray and anode ray experiments, charge to mass ratio, assertion–reason questions, and numerical problems. It is designed to test both conceptual understanding and calculation skills, which are essential for success in Class 11 Chemistry.
I am writing about this worksheet because Chapter 2 is the first real step into atomic theory and modern chemistry. Many students find this chapter challenging as it introduces new terminology, experiments, and mathematical relationships. A well-structured worksheet like this one helps students practise systematically and identify weak areas early, which is crucial for building confidence and scoring well in exams.
Overview of the Worksheet
As seen in the uploaded PDF Ch-2 structure of atom WS 1 QUE…, the worksheet is divided into multiple sections, each targeting a different level of understanding.
It includes:
• Section A – Multiple-choice questions
• Section B – Very short answer questions
• Section C – Short answer and numerical problems
• Section D and E – Assertion–Reason and passage-based questions
This pattern closely follows the CBSE examination style.
Discovery of Sub-Atomic Particles
A major focus of the worksheet is on how electrons, protons, and neutrons were discovered.
Key points tested include:
• Cathode ray discharge tube experiments
• J.J. Thomson’s determination of e/m ratio
• Millikan’s oil drop experiment for charge of electron
• Identification of positively charged particles (protons)
• Need for electrically neutral particles (neutrons)
Students are asked to match scientists with their discoveries and explain experimental outcomes.
Cathode Rays and Their Characteristics
Several MCQs and assertion–reason questions are based on cathode rays.
Important concepts include:
• Cathode rays originate from the cathode and move towards the anode
• They travel in straight lines in absence of electric and magnetic fields
• They are deflected by electric and magnetic fields
• They consist of negatively charged particles (electrons)
These ideas form the basis of understanding atomic structure.
Charge and Mass of Electron, Proton and Neutron
The worksheet repeatedly tests numerical values and relationships such as:
• Charge on electron
• Mass of electron
• Mass and charge of proton
• Neutron having no charge
Students are also asked to calculate the number of electrons present on a charged particle using given charge values.
Download this Ch-2 structure of atom WS 1 QUESTIONS PDF File: Click Here
Charge to Mass Ratio (e/m)
Another important area covered is the charge-to-mass ratio of particles.
Key learning points:
• e/m ratio of electron is constant
• e/m ratio of positive rays depends on residual gas
• Lighter particles show greater deflection
These concepts are checked through MCQs, short answers, and numericals.
Matter Waves and Wavelength
The worksheet includes questions comparing matter waves of electron, proton, neutron and alpha particle.
Students must understand that:
• For same speed, heavier particle has shorter wavelength
• Electron has the longest wavelength among these
This builds a bridge to quantum mechanics.
Assertion–Reason Questions
Assertion–Reason type questions test conceptual clarity.
Examples include:
• Cathode rays are deflected towards positive plate because they are negatively charged
• Subshells in multi-electron atoms have different energies
• Deflection depends on mass of the particle
These questions encourage logical reasoning rather than rote learning.
Numerical Problem-Solving Section
The worksheet contains numericals such as:
• Finding number of electrons from given charge
• Calculating total electrons in one mole of methane
• Finding mass and charge of one mole of electrons
• Determining number of protons or neutrons in given mass
These questions strengthen formula application and problem-solving speed.
Passage-Based Questions
Some sections provide a short passage about Faraday’s and Thomson’s experiments and ask questions based on it.
This tests:
• Reading comprehension
• Conceptual understanding
• Ability to link experiments with conclusions
Such questions are increasingly common in board exams.
Why This Worksheet Is Important for Students
From my experience, this worksheet is extremely useful because:
• It covers all major concepts of Chapter 2
• It includes different question types
• It matches CBSE exam pattern
• It builds both theory and numerical strength
Regular practice with such worksheets reduces fear of physical chemistry topics.
