Question 18
Which one of the following is a correct electronic configuration of Sodium?
- 2, 8
- 8, 2, 1
- 2, 1, 8
- 2, 8, 1
2, 8, 1
Reason — Sodium has atomic number 11 and it's electronic configuration is 2,8,1.
Key Concepts Covered
This question tests your understanding of the following concepts from the chapter Structure of the Atom: Question, Correct, Electronic, Configuration, Sodium, Structure of the Atom. These are fundamental topics in Science that students are expected to master as part of the CBSE Class 9 curriculum.
A thorough understanding of these concepts will help you answer similar questions confidently in your CBSE examinations. These topics are frequently tested in both objective and subjective sections of Science papers. We recommend revising the relevant section of your textbook alongside practising these solved examples to build a strong foundation.
How to Approach This Question
Read the question carefully and identify what is being asked. Break down complex questions into smaller parts. Use the terminology and concepts discussed in this chapter. Structure your answer logically — begin with a definition or key statement, then provide supporting details. Review your answer to ensure it addresses all parts of the question completely.
Key Points to Remember
- Read the question carefully and identify all parts before answering.
- Use the terminology specific to this subject and chapter.
- Review the textbook content for this chapter before attempting questions.
- Practice writing concise, well-structured answers within time limits.
Practice more questions from Structure of the Atom — Science, Class 9 CBSE
Chapter 4: Structure of the Atom — Quick Reference
Quick Revision Points
- Thomson: positive sphere with embedded electrons (plum pudding)
- Rutherford: nucleus (dense, positive) + electrons in orbits. Limitation: electron should spiral in
- Bohr: electrons in fixed energy levels (shells K, L, M, N)
- Max electrons per shell: 2n² (K=2, L=8, M=18, N=32); outermost max 8
- Z = protons = electrons; A = protons + neutrons; neutrons = A − Z
- Isotopes: same Z, different A. Isobars: different Z, same A
- Valency: ≤ 4 → valency = outermost e⁻; > 4 → valency = 8 − outermost e⁻
- Read the detailed chapter notes for complete coverage of all NCERT topics.
- Practice all NCERT in-text and back exercise questions — they are frequently asked in exams.
- Focus on comparison tables, diagrams, and definitions — these are high-scoring areas.
- For numericals (if applicable), practice at least 20 problems of varying difficulty.
- Refer to the practice question bank (200+ questions) for thorough preparation.
- Detailed Notes: ch04-structure-of-the-atom.html
- Practice Questions: 100+ questions with answers in 05-practice-questions/
- Chapter Test: 30-mark test paper in 06-tests/chapter-tests-30marks/
- Formula Sheet: Complete formula reference in 03-teacher-aid/formula-sheet.html