The uploaded PDF contains detailed solutions for the worksheet based on Chapter 2, Structure of Atom, for Class 11 Chemistry. This solution set explains multiple-choice questions, assertion–reason questions, short answers, and numerical problems in a clear and logical manner. Instead of just giving final answers, the PDF also includes brief explanations, formulas, and reasoning, which are extremely helpful for students who want to understand the concepts properly.
I am writing about this solutions PDF because many students practise worksheets but are unsure whether their answers are correct or not. A reliable solution guide helps students verify their work, understand mistakes, and improve accuracy. More importantly, Chapter 2 is a foundation chapter, and clarity here is essential for learning atomic models, electronic configuration, and bonding in later chapters.
What This Solutions PDF Contains
According to the uploaded solutions PDF Ch-2 structure of atom WS 1 SOL, the answers are arranged section-wise and follow the same structure as the worksheet.
It includes:
• Section A – MCQ answers with explanations
• Section B – Short-answer solutions
• Section C – Numerical problem solutions
• Section D and E – Assertion–Reason and passage-based solutions
This systematic layout makes it easy to cross-check answers.
Solutions Related to Cathode Rays and Electrons
The PDF clearly explains how cathode rays are produced at very low pressure and high voltage inside discharge tubes.
Important points covered:
• Cathode rays are streams of electrons
• They originate from the cathode and move towards the anode
• They are deflected by electric and magnetic fields
• Their characteristics do not depend on the gas or electrode material
These explanations strengthen the concept of electrons as universal particles.
Millikan’s Oil Drop Experiment Explained
The solutions mention that Millikan’s oil drop experiment was performed to determine the charge on the electron.
Key value provided:
• Charge of electron = −1.602 × 10⁻¹⁹ C
The PDF also explains how the number of electrons on a charged oil drop can be calculated using this value.
Download this Ch-2 structure of atom WS 1 SOL PDF File: Click Here
Charge to Mass Ratio (e/m) of Electron
The PDF confirms that J.J. Thomson determined the charge-to-mass ratio of the electron.
Important value:
• e/m of electron = 1.76 × 10¹¹ C/kg
It also explains why e/m of cathode rays is the same everywhere, while e/m of anode rays depends on the gas used.
Mass and Charge of Sub-Atomic Particles
The solutions clearly state:
• Mass of electron = 9.1 × 10⁻³¹ kg
• Charge of proton = +1.602 × 10⁻¹⁹ C
• Proton and neutron have nearly equal mass
• Neutron has no charge
Such values are frequently asked in exams.
Assertion–Reason Solutions
The PDF gives correct options along with explanations.
Examples include:
• Cathode rays are deflected towards positive plate because they are negatively charged
• Subshells in multi-electron atoms have different energies
• Density and deflection concepts explained logically
These help students develop reasoning skills.
Numerical Problem Solutions
The PDF contains step-by-step solutions for:
• Finding number of electrons from given charge
• Calculating mass and charge of one mole of electrons
• Finding charge and mass of lithium nucleus
• Calculating electrons in one mole of methane
• Finding protons and neutrons in given mass of substances
These worked examples improve calculation confidence.
Why This Solutions PDF Is Useful
From my experience, this solutions PDF is extremely helpful because:
• It saves time during revision
• It clears doubts quickly
• It improves conceptual clarity
• It strengthens numerical skills
Students who use it alongside NCERT perform better in tests.
