Step-by-step ICSE solutions and marking scheme for Periodic Properties & Variations from Selina Concise Chemistry (Class 10) - Dr. S.P. Singh and 5 generated practice problem sets.

Pairing Canonical Document Looking for key concepts, summary notes, formulas and ray/biological diagrams?

📘 Open Chapter Notes (class10_chemistry_periodic_properties_and_variations.html) →

Chemistry Chapter 1 1 Textbook + 5 Generated Exercises 10 - 12 Marks in ICSE Board Exam

Periodic Properties & Variations — Solved Textbook & 5 Practice Sets

Prescribed Reference Textbook: Selina Concise Chemistry (Class 10) - Dr. S.P. Singh

Canonical Link: https://icse.smartindia.pro/class10_chemistry_solved_exercise_periodic_properties_and_variations.html

Prerendered HTML Page: class10_chemistry_solved_exercise_periodic_properties_and_variations.html

📘 Prescribed Textbook Solved Exercise (Selina Concise Chemistry (Class 10))

Primary Curriculum Benchmark

Direct solution to core textbook review exercise with complete CISCE marking scheme breakdown.

Selina Chapter 1 - Review Question 15 Selina Concise Chemistry Class 10

4 Marks Allotted

Account for the following: (a) Ionisation potential increases across a period from left to right. (b) Atomic size decreases across a period.

Step-by-Step ICSE Evaluator Marking Key

Part (a) Ionisation Potential Trend

Across a period from left to right, the atomic number (nuclear charge) increases while the number of shells remains constant. Consequently, the effective nuclear pull on valence electrons increases, making it harder to remove an electron. Thus, I.P. increases.

2 Marks

Part (b) Atomic Size Trend

As nuclear charge increases across the period with no addition of extra shells, the outer electrons are pulled closer to the nucleus. Hence, atomic radius decreases.

2 Marks

Final Verified Answer: Both trends stem from increased effective nuclear charge with constant number of electron shells. (Key Units: kJ/mol, pm)

💡 Examiner Directive: Always mention TWO factors in periodic trend reasoning: (1) Nuclear charge, and (2) Number of electron shells / shielding effect.

🎯 5 Generated Practice Exercises with Step-Marking

CISCE Syllabus Graded Set

Graded from fundamental 2-mark definitions and 3-mark numerical applications to 4-mark structured and High-Order Thinking (HOTS) questions.

Generated Practice Set 1 - Core Concept (2 Marks) Difficulty: Easy

2 Marks Total

Define "Modern Periodic Law" in the context of ICSE Class 10 Chemistry. State its primary characteristic or SI unit/standard symbol.

Step-by-Step Marking Breakdown

Step 1: Precise Technical Definition

The physical and chemical properties of elements are periodic functions of their atomic numbers (Moseley).

1 Mark

Step 2: Mandatory Technical Criteria

Ensure the definition contains mandatory keywords: Periodic functions, Atomic numbers, Not atomic mass.

1 Mark

Final Answer: Accurate scientific/scholarly definition containing all mandatory ICSE evaluation keywords. (Units: Elementary charge)

💡 Examiner Directive: Avoid colloquial explanations. Use the exact technical definition given in prescribed CISCE curriculum.

Generated Practice Set 2 - Method & Application (3 Marks) Difficulty: Medium

3 Marks Total

A system governed by "Periodic Trend Across a Period (Left to Right)" has standard parameters. Using the relation Nuclear Charge ↑ | Atomic Radius ↓ | I.P. ↑ | E.A. ↑ | E.N. ↑ | Non-metallic Character ↑, calculate the required variable when other quantities are doubled. State the formula and show step-by-step substitution.

Step-by-Step Marking Breakdown

Step 1: State the Formula / Conceptual Principle

Write the primary governing equation: Nuclear Charge ↑ | Atomic Radius ↓ | I.P. ↑ | E.A. ↑ | E.N. ↑ | Non-metallic Character ↑. Define each symbol clearly.

Formula: Nuclear Charge ↑ | Atomic Radius ↓ | I.P. ↑ | E.A. ↑ | E.N. ↑ | Non-metallic Character ↑

1 Mark

Step 2: Mathematical / Procedural Deduction

Substitute the modified parameters: Let initial state be S₁ and new state be S₂. Set up the ratio S₂ / S₁ and simplify algebraically.

1 Mark

Step 3: Concluding Result & Interpretation

Express the final outcome clearly with proper units or scientific deduction.

1 Mark

Final Answer: Result derived directly from Nuclear Charge ↑ | Atomic Radius ↓ | I.P. ↑ | E.A. ↑ | E.N. ↑ | Non-metallic Character ↑ (Units: Elementary charge)

💡 Examiner Directive: In derivation and numerical questions, every intermediate mathematical step carries fractional credit.

Generated Practice Set 3 - Comparative Analysis (3 Marks) Difficulty: Medium

3 Marks Total

Differentiate between "Modern Periodic Law" and "Ionisation Potential (I.P.)" on the basis of: (i) Fundamental definition/mechanism, (ii) Key working condition or formula, (iii) Real-world practical example or application.

Step-by-Step Marking Breakdown

Point 1: Conceptual Difference

Contrast the primary mechanisms: Modern Periodic Law focuses on Periodic functions, whereas Ionisation Potential (I.P.) emphasizes Energy required.

1 Mark

Point 2: Quantitative / Operational Difference

Highlight differences in formulas, governing laws, operating environments, or physical behavior.

1 Mark

Point 3: Exemplary Differentiation

Provide one clear, unambiguous textbook example illustrating each concept under everyday conditions.

1 Mark

Final Answer: Three-point structured comparative table with clear opposing criteria. (Units: Tabular points)

💡 Examiner Directive: Always construct a comparative answer in a two-column table with an explicit "Point of Difference" header column.

Generated Practice Set 4 - Board Standard Structured (4 Marks) Difficulty: Board Expected

4 Marks Total

A comprehensive ICSE examination question based on "Periodic Properties & Variations":
(i) State the fundamental law or rule governing "Modern Periodic Law". [1 Mark]
(ii) How does this concept change with temperature / pressure / time / scale? [1 Mark]
(iii) State one common mistake students make in this chapter and provide the correct scientific reasoning. [2 Marks]

Step-by-Step Marking Breakdown

Part (i): Statement of the Law

State the formal principle verbatim as recognized by CISCE syllabus committees.

1 Mark

Part (ii): Dependency Analysis

Explain the direct or inverse variation of the target variable with respect to environmental or operational factors.

1 Mark

Part (iii): Error Analysis & Correct Resolution

Identify the frequent pitfall: Students often confuse Periodic functions with related quantities. The correct understanding requires strict application of Electronegativity (E.N.).

2 Marks

Final Answer: Structured 4-mark solution completely addressing parts (i), (ii), and (iii). (Units: Multi-part breakdown)

💡 Examiner Directive: Notice the mark distribution in multi-part questions; allocate your answering time and detail strictly in proportion to allotted marks.

Generated Practice Set 5 - Higher Order Thinking (HOTS) (4 Marks) Difficulty: Hard

4 Marks Total

A critical scenario-based problem in "Periodic Properties & Variations": An experiment is performed under non-ideal conditions involving "Modern Periodic Law" and "Ionisation Potential (I.P.)".
(a) Predict what happens to the expected outcome if the boundary condition fails.
(b) Give complete scientific justification.
(c) State the critical safeguard or correction formula to rectify the error.

Step-by-Step Marking Breakdown

Part (a): Prediction of Anomalous Outcome

Accurately predict the deviation from theoretical expectations when standard assumptions are violated.

1 Mark

Part (b): Scientific Justification

Provide a rigorous scientific explanation using first principles and mandatory keywords: Periodic functions, Atomic numbers, Not atomic mass, Energy required.

2 Marks

Part (c): Correction Protocol & Mathematical Remedy

State the exact rectification formula or procedural calibration necessary to restore accuracy.

Formula: Nuclear Charge ↑ | Atomic Radius ↓ | I.P. ↑ | E.A. ↑ | E.N. ↑ | Non-metallic Character ↑

1 Mark

Final Answer: Full scenario analysis with anomaly prediction, first-principles justification, and correction method. (Units: HOTS Analytical Reasoning)

💡 Examiner Directive: HOTS questions in ICSE evaluate depth of conceptual understanding. Avoid superficial guessing; reason backward from core laws.

🔑 Mandatory ICSE Examiner Technical Keywords Required in Solutions

Required for Step-Marking Credit

CISCE evaluators check for the explicit usage of mandatory technical terminology when scoring reasoning questions and step derivations. The table below outlines each key term, its technical description, the examiner marking directive, and the exact model answer phrasing expected in ICSE board examination solutions.

Mandatory Keyword #1 Core Definition Chapter Concept: Modern Periodic Law

1 Mark in Chemical Observation / Balanced Equation

"Periodic functions"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Periodic functions" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Periodic functions" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Modern Periodic Law, ensure "Periodic functions" is explicitly stated in the balanced explanation."

Mandatory Keyword #2 Core Definition Chapter Concept: Modern Periodic Law

1 Mark in Chemical Observation / Balanced Equation

"Atomic numbers"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Atomic numbers" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Atomic numbers" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Modern Periodic Law, ensure "Atomic numbers" is explicitly stated in the balanced explanation."

Mandatory Keyword #3 Core Definition Chapter Concept: Modern Periodic Law

1 Mark in Chemical Observation / Balanced Equation

"Not atomic mass"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Not atomic mass" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Not atomic mass" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Modern Periodic Law, ensure "Not atomic mass" is explicitly stated in the balanced explanation."

Mandatory Keyword #4 Core Definition Chapter Concept: Ionisation Potential (I.P.)

1 Mark in Chemical Observation / Balanced Equation

"Energy required"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Energy required" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Energy required" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Ionisation Potential (I.P.), ensure "Energy required" is explicitly stated in the balanced explanation."

Mandatory Keyword #5 Core Definition Chapter Concept: Ionisation Potential (I.P.)

1 Mark in Chemical Observation / Balanced Equation

"Most loosely bound electron"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Most loosely bound electron" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Most loosely bound electron" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Ionisation Potential (I.P.), ensure "Most loosely bound electron" is explicitly stated in the balanced explanation."

Mandatory Keyword #6 Core Definition Chapter Concept: Ionisation Potential (I.P.)

1 Mark in Chemical Observation / Balanced Equation

"Isolated gaseous atom"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Isolated gaseous atom" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Isolated gaseous atom" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Ionisation Potential (I.P.), ensure "Isolated gaseous atom" is explicitly stated in the balanced explanation."

Mandatory Keyword #7 Core Definition Chapter Concept: Ionisation Potential (I.P.)

1 Mark in Chemical Observation / Balanced Equation

"Units: kJ/mol or eV"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Units: kJ/mol or eV" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Units: kJ/mol or eV" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Ionisation Potential (I.P.), ensure "Units: kJ/mol or eV" is explicitly stated in the balanced explanation."

Mandatory Keyword #8 Core Definition Chapter Concept: Electronegativity (E.N.)

1 Mark in Chemical Observation / Balanced Equation

"Atom in a molecule"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Atom in a molecule" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Atom in a molecule" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Electronegativity (E.N.), ensure "Atom in a molecule" is explicitly stated in the balanced explanation."

Mandatory Keyword #9 Core Definition Chapter Concept: Electronegativity (E.N.)

1 Mark in Chemical Observation / Balanced Equation

"Attract shared pair of electrons"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Attract shared pair of electrons" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Attract shared pair of electrons" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Electronegativity (E.N.), ensure "Attract shared pair of electrons" is explicitly stated in the balanced explanation."

Mandatory Keyword #10 Core Definition Chapter Concept: Electronegativity (E.N.)

1 Mark in Chemical Observation / Balanced Equation

"Fluorine is highest (4.0)"

📘 Technical Definition & Detailed Description:

In ICSE Class 10 Chemistry (Periodic Properties & Variations), "Fluorine is highest (4.0)" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.

⚠️ CISCE Examiner Directive & Marking Rubric:

Examiners award marks specifically when "Fluorine is highest (4.0)" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).

📝 Model Answer Application (Exact Phrasing for Board Solutions):

"During the reaction in Electronegativity (E.N.), ensure "Fluorine is highest (4.0)" is explicitly stated in the balanced explanation."

⚖️ CISCE Evaluation Directives for Chemistry

Step-Mark Allocation: Every sub-step, formula statement, and intermediate substitution carries independent marks. Writing final answers without formula yields zero in Section B numericals.

Mandatory SI Units: In ICSE Science and Mathematics, omitting SI units or writing incorrect unit exponents causes automatic 1/2 mark deduction per problem.

Examiner Technical Vocabulary: CISCE evaluators look for exact prescribed terms in definitions and reasoning questions. General paraphrasing often loses full credit.

📚 Other Class 10 Chemistry Solved Exercises

Solve Exercises Interactively in the App

Bookmark questions, get real-time AI Mentor hints for tough steps, and test your exam readiness with live timed quizzes.

⚡ Practice in Interactive ICSE Hub