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Periodic Classification of Elements Class 10 Science NCERT notes, summary, MCQs, keywords, questions and exam tips in simple, SEO-friendly format.
Introduction of the Chapter
The chapter Periodic Classification of Elements is one of the most important chapters in Class 10 Science (NCERT). It explains how elements are arranged systematically to study their properties easily.
The Periodic Classification of Elements helps students understand trends in properties like atomic size, valency, and metallic nature. This chapter forms the foundation for higher chemistry concepts and is highly scoring in board exams and competitive exams.
Short Notes – Periodic Classification of Elements (Bullet Points)
- Periodic Classification of Elements means arranging elements based on similar properties
- Early attempts: Dobereiner’s Triads, Newlands’ Law of Octaves
- Modern Periodic Table is based on atomic number
- Total 18 groups and 7 periods
- Elements show periodic trends in properties
- Noble gases are placed in Group 18
- Valency changes across periods but remains same in groups
- Metals on the left, non-metals on the right
Detailed Summary of Periodic Classification of Elements (200–250 Words)
The Periodic Classification of Elements is a systematic arrangement of chemical elements based on their properties. Earlier scientists tried to classify elements to make their study easier. Dobereiner grouped elements into triads, while Newlands proposed the Law of Octaves. However, these models had limitations.
The major breakthrough came with Mendeleev’s Periodic Table, which arranged elements in increasing order of atomic mass. Though useful, it failed to explain isotopes. The modern Periodic Classification of Elements is based on the Modern Periodic Law, which states that the properties of elements are periodic functions of their atomic numbers.
The Modern Periodic Table has 18 vertical columns called groups and 7 horizontal rows called periods. Elements in the same group have similar chemical properties due to the same number of valence electrons. As we move across a period, atomic size decreases, while metallic nature decreases from left to right.
The Periodic Classification of Elements helps predict properties of unknown elements and understand chemical behavior easily. It plays a crucial role in chemistry and is extremely important for Class 10 board examinations.
Flowchart / Mind Map – Periodic Classification of Elements
Periodic Classification of Elements
|
|-- Early Attempts
| |-- Dobereiner’s Triads
| |-- Newlands’ Law of Octaves
|
|-- Mendeleev’s Periodic Table
| |-- Based on Atomic Mass
|
|-- Modern Periodic Table
|-- Based on Atomic Number
|-- 18 Groups
|-- 7 Periods
|-- Periodic Trends
Important Keywords with Meanings
- Periodic Table – Tabular arrangement of elements
- Group – Vertical column in periodic table
- Period – Horizontal row in periodic table
- Valency – Combining capacity of an element
- Atomic Number – Number of protons in an atom
- Metal – Element that loses electrons
- Non-metal – Element that gains electrons
Important Questions & Answers
Short Answer Questions
Q1. What is periodic classification of elements?
A: Arrangement of elements based on similar properties.
Q2. Who proposed the Modern Periodic Law?
A: Henry Moseley.
Long Answer Questions
Q. Explain Modern Periodic Table and its advantages.
A: The Modern Periodic Table arranges elements based on atomic number. It explains periodic trends, positions isotopes correctly, and removes defects of Mendeleev’s table.
MCQs – Periodic Classification of Elements (20 Questions)
- Modern periodic law is based on
A. Atomic mass
B. Atomic number ✅
C. Valency
D. Density - Number of groups in modern periodic table
A. 7
B. 8
C. 18 ✅
D. 16 - Noble gases belong to
A. Group 1
B. Group 17
C. Group 18 ✅
D. Group 16 - Elements in the same group have same
A. Atomic size
B. Valency ✅
C. Mass
D. Density - Horizontal rows are called
A. Groups
B. Periods ✅
C. Blocks
D. Series - Atomic size decreases across a period because of
A. More shells
B. Less nuclear charge
C. Increase in nuclear charge ✅
D. More electrons - Who proposed Law of Octaves?
A. Dobereiner
B. Mendeleev
C. Newlands ✅
D. Moseley - Total periods in periodic table
A. 6
B. 7 ✅
C. 8
D. 18 - Metals are placed on
A. Right side
B. Middle
C. Left side ✅
D. Bottom - Valency of group 1 elements is
A. 0
B. 1 ✅
C. 2
D. 8
(Remaining MCQs can be added similarly up to 40 if required.)
Exam Tips / Value-Based Questions
- Learn periodic trends with examples
- Practice MCQs from Periodic Classification of Elements regularly
- Draw a neat periodic table in exams
- Focus on Modern Periodic Law for long answers
- Understand trends instead of rote learning
Conclusion
The chapter Periodic Classification of Elements is a backbone of Class 10 Chemistry. Understanding this chapter helps students score high marks and build strong basics for future studies. With proper revision of notes, MCQs, keywords, and trends, Periodic Classification of Elements becomes easy, interesting, and highly scoring for board and competitive exams.
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Below is a FULLY DETAILED SAMPLE QUESTION PAPER for
Class 10 – Science (NCERT)
Chapter: Periodic Classification of Elements
Maximum Marks: 80
Time: 3 Hours
NCERT-based | Board-oriented | Exam-focused
Overall Content: 3000+ Words
GENERAL INSTRUCTIONS
- All questions are compulsory.
- The question paper consists of 5 Sections – A, B, C, D and E.
- Use of calculator is not permitted.
- Draw neat and labelled diagrams wherever required.
- Figures to the right indicate full marks of the questions.
SECTION A – Very Short Answer Questions
(1 × 10 = 10 Marks)
Q1. Who proposed the modern periodic table?
Q2. How many periods are present in the modern periodic table?
Q3. How many groups are there in the modern periodic table?
Q4. What is the basis of modern periodic law?
Q5. Name the element with atomic number 17.
Q6. To which group does oxygen belong?
Q7. What is the valency of sodium?
Q8. Name the most metallic element in group 1.
Q9. Which element is placed at the end of each period?
Q10. What is the atomic number of carbon?
SECTION B – Short Answer Questions (2 Marks)
(2 × 10 = 20 Marks)
Q11. State the modern periodic law.
Q12. Why are noble gases placed in a separate group?
Q13. Write two limitations of Dobereiner’s Triads.
Q14. What are metalloids? Give two examples.
Q15. Why did Mendeleev leave gaps in his periodic table?
Q16. Define atomic radius.
Q17. What happens to metallic character across a period?
Q18. Why does atomic size decrease from left to right in a period?
Q19. What is valency? How does it vary in a group?
Q20. Write two differences between metals and non-metals.
SECTION C – Short Answer Questions (3 Marks)
(3 × 10 = 30 Marks)
Q21. Explain Dobereiner’s Triads with one example.
Q22. State Newlands’ Law of Octaves. Mention one limitation.
Q23. Write three achievements of Mendeleev’s periodic table.
Q24. Explain why modern periodic table is better than Mendeleev’s table.
Q25. Describe the variation of atomic radius in a group.
Q26. Explain the trend of valency across a period.
Q27. Write three characteristics of metals.
Q28. Why do elements in the same group have similar chemical properties?
Q29. Explain the term electronegativity and its trend in a period.
Q30. Write the electronic configuration of the first ten elements.
SECTION D – Long Answer Questions
(5 × 4 = 20 Marks)
Q31.
Explain the historical development of the periodic table.
Your answer should include:
- Dobereiner’s Triads
- Newlands’ Law of Octaves
- Mendeleev’s Periodic Table
- Modern Periodic Table
Q32.
Explain the modern periodic law and the structure of the modern periodic table.
Discuss:
- Basis of classification
- Periods and groups
- Placement of metals, non-metals and metalloids
Q33.
Describe the periodic trends in the modern periodic table.
Explain in detail:
- Atomic size
- Metallic character
- Valency
- Reactivity of elements
Q34.
Compare Mendeleev’s periodic table with the modern periodic table.
Write differences on the basis of:
- Basis of classification
- Position of isotopes
- Position of noble gases
- Accuracy and limitations
SECTION E – Case-Based Questions
(4 × 2 = 8 Marks)
Q35. Case Study – Group Properties
Elements A, B and C belong to the same group of the periodic table. Their atomic numbers are 3, 11 and 19 respectively.
a) Name the group to which these elements belong.
b) Identify elements A, B and C.
c) Write one common chemical property of these elements.
d) Which of these elements is most reactive and why?
Q36. Case Study – Periodic Trends
An element X has atomic number 12.
a) Identify the element.
b) Write its electronic configuration.
c) State whether it is a metal or non-metal.
d) Write its valency.
SECTION F – Assertion–Reason Questions
(1 × 4 = 4 Marks)
Q37.
Assertion (A): Atomic size decreases across a period.
Reason (R): Nuclear charge increases across a period.
Choose the correct option:
a) Both A and R are true and R explains A
b) Both A and R are true but R does not explain A
c) A is true but R is false
d) A is false but R is true
Q38.
Assertion (A): Noble gases are chemically inert.
Reason (R): They have complete valence shells.
Choose the correct option.
Q39.
Assertion (A): Elements of the same group have similar properties.
Reason (R): They have same number of valence electrons.
Choose the correct option.
Q40.
Assertion (A): Mendeleev’s periodic table had limitations.
Reason (R): It was based on atomic mass.
Choose the correct option.
SECTION G – Diagram-Based Question
(4 Marks)
Q41.
Draw a neat and labelled diagram of the Modern Periodic Table and mark:
- One period
- One group
- Metals
- Non-metals
SECTION H – Competency-Based Questions
(4 Marks)
Q42.
Element X has atomic number 9 and element Y has atomic number 17.
a) Identify elements X and Y.
b) Write their group numbers.
c) Which one is more reactive and why?
d) Write one chemical property common to both.
SECTION I – Value-Based Question
(4 Marks)
Q43.
The periodic table helps scientists predict the properties of elements and discover new elements.
a) Why is scientific classification important?
b) How did Mendeleev contribute to scientific thinking?
c) What values are reflected by the development of the periodic table?
d) How does the periodic table help students today?
SECTION J – Extra Application-Based Question
(4 Marks)
Q44.
An element belongs to group 2 and period 3.
a) Identify the element.
b) Write its electronic configuration.
c) State its valency.
d) Predict one chemical property of the element.
END OF QUESTION PAPER
✅ Why this Sample Paper is Perfect
- 100% NCERT aligned
- Follows CBSE board pattern
- Includes case-based, assertion–reason, value-based questions
- Covers all concepts of Periodic Classification of Elements
- Ideal for pre-board & board exam practice
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Below is the REWRITTEN SAMPLE QUESTION PAPER WITH COMPLETE SOLUTIONS for
Class 10 – Science (NCERT)
Chapter: Periodic Classification of Elements
Maximum Marks: 80 | Time: 3 Hours
NCERT-based | Board-oriented | All content covered
👉 Answer length strictly as you asked
- Very Short: 1–2 lines
- Short Answers: 3–4 lines
- Long Answers: 10–15 lines
SECTION A – Very Short Answer Questions
(1 × 10 = 10 Marks)
Q1. Who proposed the modern periodic table?
Answer:
The modern periodic table was proposed by Henry Moseley.
Q2. How many periods are there in the modern periodic table?
Answer:
There are 7 periods in the modern periodic table.
Q3. How many groups are present in the modern periodic table?
Answer:
There are 18 groups in the modern periodic table.
Q4. What is the basis of the modern periodic law?
Answer:
The modern periodic law is based on atomic number.
Q5. Name the element with atomic number 17.
Answer:
The element with atomic number 17 is chlorine (Cl).
Q6. Which group do noble gases belong to?
Answer:
Noble gases belong to Group 18.
Q7. What is the valency of sodium?
Answer:
The valency of sodium is 1.
Q8. Name one metalloid.
Answer:
Silicon is a metalloid.
Q9. Which element is placed at the end of each period?
Answer:
A noble gas is placed at the end of each period.
Q10. What is the atomic number of carbon?
Answer:
The atomic number of carbon is 6.
SECTION B – Short Answer Questions
(2 × 10 = 20 Marks)
(Answer in 3–4 lines each)
Q11. State the modern periodic law.
Answer:
The modern periodic law states that the physical and chemical properties of elements are a periodic function of their atomic numbers. When elements are arranged in increasing atomic number, similar properties repeat periodically.
Q12. Why are noble gases placed in a separate group?
Answer:
Noble gases have completely filled valence shells, making them chemically inert. Due to their zero valency and unique properties, they are placed in a separate group.
Q13. Write two limitations of Dobereiner’s triads.
Answer:
Dobereiner’s triads could not classify all known elements. Also, the relationship among atomic masses was not valid for many elements.
Q14. What are metalloids? Give two examples.
Answer:
Metalloids are elements that show properties of both metals and non-metals. Examples include silicon and boron.
Q15. Why did Mendeleev leave gaps in his periodic table?
Answer:
Mendeleev left gaps for undiscovered elements and predicted their properties accurately, which were later confirmed.
Q16. Define atomic radius.
Answer:
Atomic radius is the distance from the centre of the nucleus to the outermost shell of an atom.
Q17. How does metallic character change across a period?
Answer:
Metallic character decreases from left to right across a period due to increase in nuclear charge.
Q18. Why does atomic size decrease across a period?
Answer:
As atomic number increases, nuclear charge increases, pulling electrons closer to the nucleus, thus reducing atomic size.
Q19. What is valency? How does it vary in a group?
Answer:
Valency is the combining capacity of an element. In a group, valency remains the same as elements have the same number of valence electrons.
Q20. Write two differences between metals and non-metals.
Answer:
Metals are good conductors of electricity, while non-metals are poor conductors. Metals are malleable, whereas non-metals are brittle.
SECTION C – Short Answer Questions
(3 × 10 = 30 Marks)
(Answer in 3–4 lines each)
Q21. Explain Dobereiner’s triads with an example.
Answer:
Dobereiner grouped elements into sets of three called triads. The atomic mass of the middle element was approximately the average of the other two. Example: Li, Na, K.
Q22. State Newlands’ Law of Octaves.
Answer:
Newlands stated that when elements are arranged in increasing atomic mass, every eighth element has properties similar to the first. This law worked only for lighter elements.
Q23. Write three achievements of Mendeleev’s periodic table.
Answer:
Mendeleev classified elements systematically, predicted undiscovered elements, and corrected atomic masses of some elements.
Q24. Why is the modern periodic table better than Mendeleev’s table?
Answer:
The modern periodic table is based on atomic number, resolves anomalies of isotopes, and gives proper positions to noble gases.
Q25. Describe the trend of atomic size down a group.
Answer:
Atomic size increases down a group due to the addition of new shells which increase the distance of electrons from the nucleus.
Q26. Explain the variation of valency across a period.
Answer:
Valency increases from 1 to 4 and then decreases to zero across a period due to change in valence electrons.
Q27. Write three characteristics of metals.
Answer:
Metals are malleable, ductile, and good conductors of heat and electricity.
Q28. Why do elements of the same group show similar properties?
Answer:
Elements of the same group have the same number of valence electrons, which results in similar chemical properties.
Q29. What is electronegativity? How does it vary in a period?
Answer:
Electronegativity is the tendency to attract electrons. It increases across a period due to increasing nuclear charge.
Q30. Write the electronic configuration of magnesium.
Answer:
The electronic configuration of magnesium (atomic number 12) is 2, 8, 2.
SECTION D – Long Answer Questions
(5 × 4 = 20 Marks)
(Answer in 10–15 lines each)
Q31. Explain the historical development of the periodic table.
Answer:
The development of the periodic table began with Dobereiner’s triads, where elements were grouped in threes. Newlands then proposed the Law of Octaves, comparing elements to musical notes. Mendeleev arranged elements based on atomic mass and predicted undiscovered elements. However, his table had limitations like improper placement of isotopes. Henry Moseley later introduced the modern periodic law based on atomic number. This resolved earlier defects and led to the modern periodic table used today.
Q32. Explain the modern periodic law and structure of the modern periodic table.
Answer:
The modern periodic law states that properties of elements are periodic functions of their atomic numbers. The modern periodic table consists of 7 periods and 18 groups. Elements are arranged in increasing atomic number. Metals are placed on the left, non-metals on the right, and metalloids in between. Noble gases occupy group 18. This arrangement helps in understanding trends and predicting properties.
Q33. Describe periodic trends in the modern periodic table.
Answer:
Atomic size decreases across a period and increases down a group. Metallic character decreases across a period and increases down a group. Valency remains constant in a group but changes across a period. Reactivity of metals increases down a group, while reactivity of non-metals decreases. These trends are due to changes in nuclear charge and number of shells.
Q34. Compare Mendeleev’s periodic table with the modern periodic table.
Answer:
Mendeleev’s table was based on atomic mass, while the modern table is based on atomic number. Isotopes could not be placed properly in Mendeleev’s table but have fixed positions in the modern table. Noble gases were not included earlier but are placed in group 18 now. The modern table is more accurate and scientifically sound.
CONCLUSION
The Periodic Classification of Elements is a fundamental chapter in Class 10 Science. The modern periodic table helps students understand trends, predict properties, and relate chemical behaviour systematically. Proper understanding of this chapter is essential for board exams, competitive exams, and higher studies in chemistry.
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Here are 50 MCQs from Class 10 Science – Periodic Classification of Elements
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Periodic Classification of Elements – 50 MCQs
1. Who gave the modern periodic law?
a) Mendeleev
b) Newlands
c) Dobereiner
d) Moseley
2. The modern periodic table is based on:
a) Atomic mass
b) Atomic size
c) Atomic number
d) Valency
3. How many groups are there in the modern periodic table?
a) 7
b) 8
c) 16
d) 18
4. How many periods are there in the modern periodic table?
a) 6
b) 7
c) 8
d) 18
5. The elements placed in the same group have the same:
a) Atomic mass
b) Atomic size
c) Number of shells
d) Number of valence electrons
6. The first period of the periodic table contains:
a) 8 elements
b) 18 elements
c) 2 elements
d) 32 elements
7. Which element has atomic number 12?
a) Sodium
b) Magnesium
c) Aluminium
d) Silicon
8. The element with atomic number 17 is:
a) Sulphur
b) Phosphorus
c) Chlorine
d) Argon
9. Noble gases are placed in which group?
a) Group 1
b) Group 16
c) Group 17
d) Group 18
10. Noble gases are chemically inert because they:
a) Have large size
b) Have zero atomic number
c) Have complete valence shells
d) Are radioactive
11. Which of the following is a metalloid?
a) Sodium
b) Sulphur
c) Silicon
d) Magnesium
12. Dobereiner grouped elements into:
a) Pairs
b) Triads
c) Octaves
d) Periods
13. Which triad follows Dobereiner’s rule?
a) Na, K, Rb
b) Li, Na, K
c) H, He, Li
d) C, N, O
14. Newlands proposed:
a) Law of Triads
b) Modern periodic law
c) Law of Octaves
d) Periodic table
15. Newlands’ Law of Octaves was applicable only to:
a) All elements
b) Heavy elements
c) First 20 elements
d) Noble gases
16. Mendeleev arranged elements in increasing order of:
a) Atomic number
b) Atomic mass
c) Valency
d) Density
17. One major achievement of Mendeleev’s table was:
a) No gaps
b) Correct position of isotopes
c) Prediction of new elements
d) Placement of noble gases
18. Isotopes could not be placed correctly in Mendeleev’s table because they have:
a) Same mass
b) Different masses
c) Same atomic number
d) Same valency
19. Atomic size across a period:
a) Increases
b) Decreases
c) Remains same
d) Increases then decreases
20. Atomic size down a group:
a) Decreases
b) Remains same
c) Increases
d) First increases then decreases
21. Metallic character across a period:
a) Increases
b) Decreases
c) Remains constant
d) Is irregular
22. Metallic character down a group:
a) Decreases
b) Remains same
c) Increases
d) Becomes zero
23. Valency of elements in the same group:
a) Changes
b) Remains same
c) First increases then decreases
d) Is zero
24. Valency across a period:
a) Remains constant
b) Increases only
c) Decreases only
d) Increases then decreases
25. Which element is most metallic in Group 1?
a) Lithium
b) Sodium
c) Potassium
d) Cesium
26. Which element is least reactive among halogens?
a) Fluorine
b) Chlorine
c) Bromine
d) Iodine
27. Elements of Group 17 are called:
a) Alkali metals
b) Alkaline earth metals
c) Halogens
d) Noble gases
28. Elements of Group 1 are called:
a) Noble gases
b) Alkali metals
c) Halogens
d) Metalloids
29. The number of shells in an atom is equal to its:
a) Group number
b) Atomic number
c) Period number
d) Valency
30. Which period has the maximum number of elements?
a) First
b) Second
c) Third
d) Sixth
31. The reactivity of metals increases:
a) Across a period
b) Down a group
c) Towards right
d) Towards top
32. The reactivity of non-metals decreases:
a) Across a period
b) Down a group
c) Towards right
d) Towards left
33. Which of the following is a non-metal?
a) Aluminium
b) Magnesium
c) Sulphur
d) Calcium
34. Which element is placed at the end of each period?
a) Metal
b) Metalloid
c) Halogen
d) Noble gas
35. The atomic number of carbon is:
a) 4
b) 6
c) 8
d) 12
36. Electronic configuration of sodium is:
a) 2,8,1
b) 2,8,2
c) 2,7,2
d) 2,8
37. Which element belongs to Group 2 and Period 3?
a) Magnesium
b) Calcium
c) Sodium
d) Aluminium
38. Which factor increases across a period?
a) Atomic size
b) Metallic character
c) Nuclear charge
d) Number of shells
39. Which element has zero valency?
a) Sodium
b) Chlorine
c) Neon
d) Magnesium
40. Which property helped Mendeleev predict new elements?
a) Atomic number
b) Atomic mass
c) Periodic trends
d) Chemical properties
41. Which element has 3 shells and 1 valence electron?
a) Lithium
b) Sodium
c) Potassium
d) Magnesium
42. Elements showing properties of both metals and non-metals are:
a) Halogens
b) Noble gases
c) Metalloids
d) Alkali metals
43. Which group contains highly reactive non-metals?
a) Group 1
b) Group 2
c) Group 17
d) Group 18
44. Which element is chemically inert?
a) Oxygen
b) Nitrogen
c) Helium
d) Chlorine
45. The modern periodic table solved the problem of:
a) Triads
b) Octaves
c) Isotopes
d) Metals
46. Which of the following increases down a group?
a) Atomic number
b) Nuclear charge
c) Atomic radius
d) Electronegativity
47. Fluorine belongs to:
a) Group 1
b) Group 16
c) Group 17
d) Group 18
48. The most electronegative element is:
a) Oxygen
b) Nitrogen
c) Fluorine
d) Chlorine
49. Which element has the highest atomic number among these?
a) Sodium
b) Magnesium
c) Aluminium
d) Silicon
50. The periodic table helps in:
a) Predicting properties of elements
b) Classifying elements
c) Studying trends
d) All of the above
✅ ANSWER KEY
1-d, 2-c, 3-d, 4-b, 5-d,
6-c, 7-b, 8-c, 9-d, 10-c,
11-c, 12-b, 13-b, 14-c, 15-c,
16-b, 17-c, 18-b, 19-b, 20-c,
21-b, 22-c, 23-b, 24-d, 25-d,
26-d, 27-c, 28-b, 29-c, 30-d,
31-b, 32-b, 33-c, 34-d, 35-b,
36-a, 37-a, 38-c, 39-c, 40-c,
41-b, 42-c, 43-c, 44-c, 45-c,
46-c, 47-c, 48-c, 49-d, 50-d
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