CBSE Class 9 Science, Structure of Atom: Important topics and questions

Important topics & questions for CBSE Class 9 Science chapter 4, Structure of Atom, are available here. All the questions have been prepared to cover most of the important topics included in the chapter. The questions and terms mentioned in this article will surely help to make your preparation easy and organised for CBSE Class 9 Science Exam, 2017-2018.

Structure of atom important questions, Class 9 Science Important QuestionsGet the CBSE Class 9th Science chapter 4, Structure of Atom: Important topics and questions to prepare for Class 9 Science Examination, 2017-2018. This will provide you with a very clear idea about what type of questions are being framed for the exam and from which topics. The pattern in which the question paper is set is quite different from the style in which the course structure is actually defined. Consider the below mentioned terms/questions at the time of preparation.

Check out the important terms/topics while preparing chapter-Structure of Atom:

• How are atoms of one element different from the atoms of another element?

• Sub atomic particles and various models related to this model

• The important postulates of Dalton’s atomic theory

• Atomic masses of subatomic particles and charges on them

• What are canal rays? Properties of canal rays

• Name of the discoverer of sub-atomic particles like electrons, protons, and neutrons

• Thomson model and postulates

• Rutherford’s model and Rutherford model experiment

• Difference between alpha particle and helium atom

• Why did Rutherford take gold foil for the experiment

• Alpha particle scattering experiment with diagram. Conclusion of the experiment-Important topic for the exam

• Who gave the nuclear model of an atom

• Who discovered the nucleus?

• Important features of nuclear model of the atom given by Rutherford

• Drawbacks of Rutherford’s model of the atom

• Revolving electron should fall in the nucleus but it is not so. Why?

• Who came forward to overcome the objection raised against Rutherford’s model of the atom?

• Postulates about the model of an atom

• What do you understand by the term ‘discrete orbit?’

• What do you think would be the observation if the α-particle scattering experiment is carried out using a foil of a metal other than gold?


Explain the meaning of arrows in different directions

• Draw a sketch of Bohr’s model of an atom with three shells.

• Neutrons are present in the nucleus of all atoms, except hydrogen. Important

• Helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have?

• Concept of distribution of electrons in different orbit or shell

• How to calculate the maximum number of electrons in a shell

• What do you mean by the term `Energy Level Index`

• What can be the maximum number of electrons in the outermost orbit?

• Do a good practice to write the distribution of electrons for different elements like carbon and sodium

• Learn entire content in the given table


• Definition of velancy and concept to write the chemical formula

• Cross velancy concept

• Explain the symbol 14N7

• How will you find the valency of chlorine, sulphur, and magnesium?

• If number of electrons in an atom is 8 and number of protons is also 8, then (i) What is the atomic number of the atom? and (ii) What is the charge on the atom?

• Concept of atomic number and mass number

• Different numerical to calculate the number of electron, proton, and neutron

• Difference between isotopes and isobars along with the examples

• Application of isotopes and isobars

Important Questions are as below:

Q. Complete mass of an atom is concentrated in the__________.

1. Protons

2. Electrons

3. Nucleus

4. Neutrons

Q. An atom has a mass number of 23 and atomic number 11. The number of protons is _________.

1. 11

2. 12

3. 23

4. 44

Q. The K, L, and M shells of an atom are full. Its atomic number is _______.

1. 18

2. 20

3. 10

4. 12

Q. Cathode rays are deflected towards__________.

1. Positive electrode

2. Negative electrode

3. Both electrodes

4. None of the electrodes

Q.  Carbon-12 atom has_______________.

1. 6 electrons, 6 protons, 6 neutrons

2. 6 electrons, 12 protons, 6 neutrons

3. 12 electrons, 6 protons, 6 neutrons

4. 18 electrons, 6 protons, 6 neutrons

Q. Energy is ________ when an electron jumps from higher energy level to lower energy level

1. Absorbed

2. Released

3. Neither absorbed nor released

4. Both 1 and 2

Q. Isotopes have different number of

1. Protons

2. Electron

3. Neutron

4. A.O.T

Q. What are the limitations of Rutherford’s model of the atom?

Q. Compare all the proposed models of an atom given in this chapter.

Q. If bromine atom is available in the form of, say, two isotopes 35Br79 (49.7%) and 35Br81 (50.3%), calculate the average atomic mass of bromine atom.

Composition of the nuclei of two atomic species X and Y are given as under:

                      X           Y

Protons =       6            6

Neutrons =     6            8

Give the mass numbers of X and Y. What is the relation between the two species?

If you have any Question/Point on the above information, please ask/discuss it in the CBSE Group

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