Question

Class 9 Science MCQ Questions of Structure of the Atom with Answers?

Answer 1

Class 9 Science MCQ Questions of  Structure of Atoms with Answers, and builds the foundation of understanding the subject.  You should be well versed with the fundamentals of elements and molecules.

Here, you will find MCQ Questions of the Structure of Atoms chapter so that you can test your knowledge. This will boost your confidence in cracking the exam with better grades as well.  MCQ Questions for class 9 Science deals with various questions that cover the basics similarly because of the advanced concepts.

Practice MCQ Questions for class 9 Chapter-Wise

1. Which of the following correctly represents the electronic distribution in the Mg atom?

(a) 3, 8, 1
(b) 2, 8, 2
(c) 1, 8, 3
(d) 8, 2, 2

2. The ion of an element has 3 positive charges. Mass number of the atom is 27 and the number of neutrons is 14. What is the number of electrons in the ion?

(a) 13
(b) 10
(c) 14
(d) 16

3. The first model of an atom was given by

(a) N. Bohr
(b) E. Goldstein
(c) Rutherford
(d) J.J. Thomson

4. An atom with 3 protons and 4 neutrons will have a valency of

(a) 3
(b) 7
(c) 1
(d) 4

5. Which of the following isotope is used in the treatment of blood cancer?

(a) P-32
(b) I-131
(c) Co-60
(d) any of these

6. When alpha-particles are sent through a thin metal foil, most of them go straight through the foil because 

(a) alpha-particles are positively charged
(b) alpha-particles are much smaller than electrons
(c) alpha-particles move with low velocity
(d) most part of the atom is empty

7. The number of electrons in an atom of Fluorine is 9. Its electronic configuration is ......

(a) 8, 1
(b) 7, 2
(c) 2, 7
(d) 1, 8

8. N shell can have a maximum of ............ electrons.

(a) 32
(b) 2
(c) 18
(d) 8

9. If Z = 6, what would be the valency of the element?

(a) 6
(b) 2
(c) 4
(d) 8

10. Argon has the atomic number of 18 and a mass number of 40. Calcium has atomic 20 and mass number 40. Calcium and argon are examples of ............

(a) isotopes
(b) isobars
(c) isotones
(d) isochores

11. The maximum number of electrons that can be accommodated in an orbit is given by the formula ........where n is the number of orbits.​

(a) 2n + 2
(b) 2(n + 2)
(c) 2/n²
(d) 2n²

12. According to J.J Thomson, an atom is a positively charged sphere. Which sub-atomic particles are embedded in it?

(a) Electrons
(b) Canal Rays
(c) Protons
(d) Neutrons

13. What are the essential conditions for the production of anode rays?

(a) High voltage and low pressure
(b) High voltage and high pressure
(c) Low voltage and high pressure
(d) Low voltage and low pressure

14. What is the charge of anode rays?

(a) Negative 
(b) Positive
(c) Neutral
(d) Zero

15. Which symbols are used to represent different Bohr’s orbits?

(a) K, L, M, N
(b) O, P, Q, R
(c) A B, C, D
(d) W, X, Y, Z

16. The isotope of hydrogen that contains the same number of protons and neutrons in its nucleus is called

(a) Protium
(b) Deuterium
(c) Tritium
(d) None of these

17.  An element has electronic configuration 2,8,4 it will be classified as

(a) Metal
(b) Non-metal
(c) Metalloid
(d) None of these

18. The valence electrons of an element are responsible for

(a) Physical properties of an element
(b) Chemical properties of an element
(c) Both the properties
(d) None of these

19. ₇N¹⁵ and ₈O¹⁶ are a pair of

(a) Isotopes
(b) Isobars
(c) Isotones
(d) None of these

20. Neutron Possesses

(a) Positive charge
(b) No charge
(c) Negative charge
(d) None of the above.

Answer 2

1. Answer : (b) 2, 8, 2

Explanation: Atomic number and the number of electrons in magnesium atom is 12. So, electronic configuration is 2, 8, 2 (because 12 = 2 + 8 + 2).

2. Answer : (b) 10

Explanation: Atomic number = mass number – number of neutrons 

= 27-14 

= 13 

This is the atomic number of aluminium. Therefore, this element is aluminium (Al). Number of electrons in the Al atom = 13 Number of electrons in the AI³⁺ ion.

= 13 – 3

 = 10. 

As it is formed from the neutral atom by loss of 3 electrons.

3. Answer : (d) J.J. Thomson

Explanation: Sir J.J Thomson gave the first model of the atom. He by means of a cathode-ray experiment discovered the existence of negatively charged particles in an atom which led to the discovery of electrons.

4. Answer : (c) 1

Explanation: Mass number = Number of protons + number of neutrons 

=3 + 4 

= 7.

Hence, its valency is 1.

5. Answer : (a) P-32

Explanation: Phosphorus P 32. A radioactive form of the element phosphorus. It is used in the laboratory to label DNA and proteins. It has also been used to treat a blood disorder called polycythemia vera and certain types of leukemia, but it is not commonly used anymore.

6. Answer : (b) alpha-particles are much smaller than electrons

Explanation: Alpha particles being positively charged do not move straight through the foil. They move straight due to a lot of empty spaces in the atom.

7. Answer : (c) 2, 7

Explanation: Fluorine is the ninth element with a total of 9 electrons. In writing the electron configuration for fluorine the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for F go in the 2s orbital. The remaining five electrons will go in the 2p orbital.

8. Answer : (a) 32

Explanation: N shell can have a maximum of 32 electrons.

9. Answer : (c) 4

Explanation: The electronic configuration of the element is 2,4. Since it has 4 electrons in its outermost (valence) shell so, the valency of the element is 4.

10. Answer : (b) isobars

Explanation: Isotopes are atomic structures of same elements having a different mass number/atomic mass. Isobars are different chemical elements having same atomic mass. Atomic numbers of all isotopic forms of a single element are equal. Atomic numbers of isobars vary from each other.

11. Answer : (d) 2n²

Explanation: The maximum number of electrons that can be accommodated in an orbit is given by the formula 2n² where n is the number of orbit.

12. Answer : (a) Electrons

Explanation: Though several alternative models were advanced in the 1900s by Kelvin and others, Thomson held that atoms are uniform spheres of positively charged matter in which electrons are embedded.

13. Answer : (a) High voltage and low pressure

Explanation: The essential conditions for the production of anode rays is high voltage and very low pressure in a discharge tube.

14. Answer : (b) Positive

Explanation: Anode rays consist of material particles. Anode rays are deflected by an electric field towards a negatively charged plate. This indicates that they are positively charged.

15. Answer : (a) K, L, M, N

Explanation: According to the postulate of Neils Bohr, “electrons revolve around the centre of an atom (nucleus) in a predictable pathway named orbits”. The representation of the orbits is done by letters and numbers such as K, L, M, N, O, and 1,2,3,4 respectively.

16. Answer : (b) Deuterium

Explanation: Protium is the most prevalent hydrogen isotope, with an abundance of 99.98%. It consists of one proton and one electron. It is typically not found in its monoatomic form, but bonded with itself (H₂) or other elements. Deuterium is a hydrogen isotope consisting of one proton, one neutron, and one electron.

17. Answer : (c) Metalloid

Explanation: An element with the electronic configuration is 2, 8, 4 has electronegativity in between non-metal and metal. So it can be classified as a metalloid.

18. Answer : (b) Chemical properties of an element

Explanation: Valence electrons determine whether they will readily bond with other elements or not. It also determines the number of bonds formed and also the atom's charge. And these are the chemical properties of an atom. Therefore valence electrons are responsible for the chemical properties of an element.

19. Answer : (c) Isotones

Explanation: Isotones are atomic species that share the same number of neutrons and differ in the number of protons. Examples of isotones include carbon-12, nitrogen-13, and oxygen-14. These atoms all have six neutrons and six, seven, and eight protons respectively.

20. Answer : (b) No charge

Explanation: A neutron has no net charge because the charge of the quarks that make up the neutron balance each other out.

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