CBSE Class 9 > Class 9 Notes > Science > Unit Test: Structure of the Atom
Unit Test: Structure of the Atom
Time: 1 hour
M.M. 30
Attempt all questions.
Question numbers 1 to 5 carry 1 mark each.
Question numbers 6 to 8 carry 2 marks each.
Question numbers 9 to 11 carry 3 marks each.
Question numbers 12 & 13 carry 5 marks each.
Q1. What are canal rays? (1 Mark)
Q2. What is the charge of an atom with one electron and one proton? (1 Mark)
Q3. Which subatomic particle was discovered by J. Chadwick? (1 Mark)
Q4. What is the maximum number of electrons in the K-shell? (1 Mark)
Q5. Which model of the atom compares it to a Christmas pudding? (1 Mark)
Q6. State two features of Rutherford's model of the atom. (2 Marks)
Q7. How is the valency of fluorine determined? (2 Marks)
Q8. Differentiate between atomic number and mass number. (2 Marks)
Q9. Explain the limitations of Thomson's model of the atom. (3 Marks)
Q10. Describe Bohr's model of the atom with its postulates. (3 Marks)
Q11. What are isotopes? Explain with two examples. (3 Marks)
Q12. Explain Rutherford's alpha-particle scattering experiment and its conclusions. (5 Marks)
Q13. Complete the table for the given atomic species and identify their relationship. (5 Marks)
The document Unit Test: Structure of the Atom is a part of the Class 9 Course Science Class 9.
All you need of Class 9 at this link: Class 9
FAQs on Unit Test: Structure of the Atom
| 1. What is the basic structure of an atom? |  |
Ans. An atom consists of a nucleus at its center, which contains protons and neutrons. Protons are positively charged particles, while neutrons have no charge. Surrounding the nucleus are electrons, which are negatively charged particles that orbit the nucleus in electron shells. The number of protons in the nucleus determines the element's atomic number and its identity.
| 2. Who proposed the first atomic model and what were its key features? | |
Ans. The first atomic model was proposed by John Dalton in the early 19th century. Dalton's model suggested that atoms are indivisible and indestructible particles, which combine in fixed ratios to form compounds. He also proposed that all atoms of a given element are identical in mass and properties, laying the groundwork for modern atomic theory.
| 3. How do the mass and charge of subatomic particles compare? | |
Ans. Protons have a positive charge of +1 and a relative mass of 1 atomic mass unit (amu). Neutrons are neutral (no charge) and have a similar mass of approximately 1 amu. Electrons have a negative charge of -1 and a much smaller mass, about 1/1836 of a proton's mass. This significant difference in mass is why the mass of an atom is primarily determined by the number of protons and neutrons in the nucleus.
| 4. What is the significance of the atomic number and mass number? | |
Ans. The atomic number is the number of protons in the nucleus of an atom and defines the element. For example, hydrogen has an atomic number of 1, while carbon has an atomic number of 6. The mass number, on the other hand, is the total number of protons and neutrons in the nucleus. It is used to identify isotopes, which are variants of an element that have the same number of protons but different numbers of neutrons.
| 5. What are isotopes and why are they important? | |
Ans. Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different mass numbers. For example,¹²C and ¹³C are isotopes of carbon. Isotopes are important in various fields, including medicine (for imaging and cancer treatment), archaeology (carbon dating), and nuclear energy. Their unique properties allow scientists to use them for specific applications based on their stability or radioactivity.
About this Document
4.87/5 Rating
Apr 18, 2026 Last updated
Document Description: Unit Test: Structure of the Atom for Class 9 2026 is part of Science Class 9 preparation. The notes and questions for Unit Test: Structure of the Atom have been prepared according to the Class 9 exam syllabus. Information about Unit Test: Structure of the Atom covers topics like and Unit Test: Structure of the Atom Example, for Class 9 2026 Exam. Find important definitions, questions, notes, meanings, examples, exercises and tests below for Unit Test: Structure of the Atom.
Introduction of Unit Test: Structure of the Atom in English is available as part of our Science Class 9 for Class 9 & Unit Test: Structure of the Atom in Hindi for Science Class 9 course. Download more important topics related with notes, lectures and mock test series for Class 9 Exam by signing up for free. Class 9: Unit Test: Structure of the Atom
Description
Unit Test: Structure of the Atom of Science Class 9 - variety of important questions with solutions, helping you prepare for exam. Download free PDF from EduRev.
Information about Unit Test: Structure of the Atom
In this doc you can find the meaning of Unit Test: Structure of the Atom defined & explained in the simplest way possible. Besides explaining types of Unit Test: Structure of the Atom theory, EduRev gives you an ample number of questions to practice Unit Test: Structure of the Atom tests, examples and also practice Class 9 tests
Related Searches
Viva Questions, Important questions, Summary, study material, Free, Objective type Questions, ppt, Unit Test: Structure of the Atom, Previous Year Questions with Solutions, practice quizzes, shortcuts and tricks, past year papers, pdf , Extra Questions, Unit Test: Structure of the Atom, Sample Paper, MCQs, Unit Test: Structure of the Atom, Semester Notes, video lectures, mock tests for examination, Exam;