ICSE Class 9 Atomic Structure and Chemical Bonding Questions and Answers

 ICSE Class 9  Atomic Structure and Chemical Bonding Questions

ICSE Class 9: Atomic Structure & Chemical Bonding Q&A

Strengthen your concepts with these important exam-oriented questions on Atomic Structure and Chemical Bonding. This guide covers subatomic particles, electronic configuration, valency, and the formation of ionic and covalent bonds.

ICSE Class 9 Chemistry Practice Questions

This worksheet is an essential resource for ICSE Class 9 students aiming to master the fundamental concepts of Chemistry. It covers two critical chapters: Atomic Structure and Chemical Bonding. The questions are structured to test your understanding of subatomic particles, atomic number, mass number, electronic configuration, valency, the octet rule, and types of chemical bonds (electrovalent and covalent).

Part 1: Comprehensive Exam-Style Questions

Section A: Multiple Choice Questions (10 Marks)

1. The atoms of the same element having identical chemical properties but different atomic mass are called:
   (a) Valency (b) Isotopes (c) Mass number (d) Atomic number
2. An ion is formed by:
   (a) Losing an electron (b) Gaining an electron (c) Losing or gaining an electron (d) Losing or gaining a proton
3. The mass number of an atom is given by the sum of:
   (a) Neutrons and protons (b) Electrons and protons (c) Neutrons and electrons (d) Electrons, protons and neutrons
4. An electron moves around the nucleus in a fixed path called:
   (a) Orbit (b) Shell (c) Energy level (d) All of the above
5. Which of the following describes the formation of an ionic bond?
   (a) Sharing of electrons (b) Transfer of electrons (c) Sharing of protons (d) Transfer of neutrons
6. An atom contains 5 electrons, 5 protons and 6 neutrons. The atomic number of the atom is:
   (a) 10 (b) 11 (c) 16 (d) 5
7. The electronic configuration 2, 8, 2 is for the element:
   (a) Calcium (b) Magnesium (c) Sulphur (d) Potassium
8. Covalent compounds are generally formed by the:
   (a) Transfer of electrons between a metal and a non-metal (b) Sharing of electrons between two non-metals (c) Transfer of electrons between two non-metals (d) Sharing of electrons between a metal and a non-metal
9. Which of the following is an example of an ionic compound?
   (a) H₂O (b) CH₄ (c) N₂ (d) NaCl
10. Rutherford's alpha particle scattering experiment led to the discovery of:
    (a) Electrons (b) Protons (c) Nucleus (d) Neutrons

View Answer Key – Section A

1. (b) Isotopes
2. (c) Losing or gaining an electron
3. (a) Neutrons and protons
4. (d) All of the above
5. (b) Transfer of electrons
6. (d) 5 (Atomic number = number of protons)
7. (b) Magnesium (Atomic number = 2+8+2 = 12)
8. (b) Sharing of electrons between two non-metals
9. (d) NaCl
10. (c) Nucleus

Section B: Fill in the Blanks (5 Marks)

1. The number of protons in the nucleus of an atom is called its ________.
2. Hydrogen has three isotopes namely ________, ________, and ________.
3. An element with 2 electrons in its outermost shell is typically a ________.
4. Ionic bonds are formed by the ________ of electrons.
5. Covalent bonds are formed by the ________ of electrons.

View Answer Key – Section B

1. atomic number
2. Protium, Deuterium, and Tritium
3. metal
4. transfer
5. sharing

Section C: Short Answer Questions (18 Marks)

(Answer any six questions. Each question carries 3 marks.)

16. State what is meant by the following terms: (a) Atomic number (b) Mass number (c) Orbits

17. Define an isotope. Give a reason why isotopes have the same chemical but different physical properties.

18. Define Ionic/Electrovalent bond and Covalent bond.

19. Write down the number of neutrons in an atom having atomic number 17 and mass number 37.

20. Describe the discovery of subatomic particles: electron, proton, and neutron. Mention the scientist and experiment related to each.

21. Five atoms are labelled V(20,40), W(9,19), X(3,7), Y(7,16), Z(14,28). Answer: (i) Which one has configuration 2,7? (ii) Write the formula of the compound formed between X & Y.

22. Write the symbol, electronic configuration, and atomic number of the following elements: (a) Hydrogen, (b) Lithium, (c) Carbon, (d) Oxygen, (e) Sodium, (f) Magnesium, (g) Aluminium, (h) Phosphorus, (i) Chlorine, (j) Calcium.

23. State the main postulates of Dalton's atomic theory. How does the modern atomic theory contradict and confirm Dalton's atomic theory?

24. Write the number of protons, electrons, and neutrons in the following isotopes: (i) ³⁵₁₇Cl (ii) ³⁷₁₇Cl

View Answer Key – Section C

16. (a) Atomic Number (Z): The number of protons in the nucleus of an atom. (b) Mass Number (A): The total number of protons and neutrons in the nucleus of an atom. (c) Orbits: The fixed circular paths in which electrons revolve around the nucleus.

17. Isotopes are atoms of the same element with the same atomic number but different mass numbers. They have the same chemical properties because chemical properties depend on the number of electrons, which is the same. They have different physical properties (like mass, density) because they have different numbers of neutrons.

18. Ionic Bond: The chemical bond formed by the complete transfer of one or more electrons from a metal atom to a non-metal atom. Covalent Bond: The chemical bond formed by the mutual sharing of one or more pairs of electrons between two atoms, usually non-metals.

19. Number of neutrons = Mass number - Atomic number = 37 - 17 = 20 neutrons.

20. Electron: Discovered by J.J. Thomson through the Cathode Ray Tube experiment. Proton: Discovered by E. Goldstein (canal rays), but credited to Rutherford who identified it as the nucleus of a hydrogen atom. Neutron: Discovered by James Chadwick by bombarding beryllium with alpha particles.

21. (i) Atom W (Atomic No. 9) has the electronic configuration 2, 7. (ii) Atom X is Lithium (2, 1) with valency +1. Atom Y is Nitrogen (2, 5) with valency -3. The formula of the compound is Li₃N (Lithium Nitride).

22. (a) H: 1, (1) (b) Li: 3, (2,1) (c) C: 6, (2,4) (d) O: 8, (2,6) (e) Na: 11, (2,8,1) (f) Mg: 12, (2,8,2) (g) Al: 13, (2,8,3) (h) P: 15, (2,8,5) (i) Cl: 17, (2,8,7) (j) Ca: 20, (2,8,8,2).

23. Dalton's Postulates: 1. Matter consists of indivisible atoms. 2. Atoms of the same element are identical. 3. Atoms of different elements are different. 4. Atoms combine in simple whole-number ratios. Contradictions: Atoms are divisible (protons, neutrons, electrons). Isotopes show that atoms of the same element can have different masses. Confirmations: The atom is still the smallest unit participating in a chemical reaction, and they combine in fixed ratios.

24. (i) ³⁵₁₇Cl: Protons=17, Electrons=17, Neutrons=18 (35-17). (ii) ³⁷₁₇Cl: Protons=17, Electrons=17, Neutrons=20 (37-17).

Section D: Show the formation of following elements or compounds (7 Marks)

(Answer any four)

(a) Sodium chloride (b) Water (c) Methane (d) Magnesium oxide (e) Nitrogen

View Answer Key – Section D

(Note: These are best shown with Lewis dot diagrams.)

(a) Sodium chloride (NaCl): Ionic bond. Sodium (2,8,1) transfers its one valence electron to Chlorine (2,8,7). Na becomes Na⁺ and Cl becomes Cl^-.

(b) Water (H₂O): Covalent bond. One Oxygen atom (2,6) shares one electron with each of the two Hydrogen atoms, forming two single covalent bonds.

(c) Methane (CH₄): Covalent bond. One Carbon atom (2,4) shares one electron with each of the four Hydrogen atoms, forming four single covalent bonds.

(d) Magnesium oxide (MgO): Ionic bond. Magnesium (2,8,2) transfers its two valence electrons to Oxygen (2,6). Mg becomes Mg²⁺ and O becomes O^2-.

(e) Nitrogen (N₂): Covalent bond. Two Nitrogen atoms (2,5) share three pairs of electrons with each other to form a triple covalent bond.

Part 2: Additional Practice Questions

Section A – Multiple Choice Questions (MCQs)

1. The subatomic particle with no charge is the: a) Proton b) Electron c) Neutron d) Nucleus
2. An element has an electronic configuration of 2, 8, 7. Its valency is: a) 1 b) 2 c) 7 d) 8
3. Which of the following molecules contains a double covalent bond? a) Methane (CH₄) b) Oxygen (O₂) c) Chlorine (Cl₂) d) Ammonia (NH₃)

View Answer Key – Section A

1. c) Neutron
2. a) 1 (It needs one electron to complete its octet)
3. b) Oxygen (O₂)

Section B – Differentiate Between

1. Atom and Ion: Differentiate based on charge and number of electrons.
2. Electrovalent and Covalent Compounds: Differentiate based on their state, melting point, and conductivity.
3. Isotopes and Isobars: Differentiate based on atomic number and mass number.

View Answer Key – Section B

1. Atom: Electrically neutral; number of protons equals the number of electrons. Ion: Electrically charged; has an unequal number of protons and electrons.
2. Electrovalent Compounds: Usually crystalline solids, high melting points, conduct electricity in molten/aqueous state. Covalent Compounds: Can be solids, liquids or gases; low melting points, generally do not conduct electricity.
3. Isotopes: Same atomic number, different mass number (e.g., ¹²C, ¹⁴C). Isobars: Same mass number, different atomic number (e.g., ⁴⁰Ar, ⁴⁰Ca).

Section C – Diagram-Based Questions

1. Draw the orbital diagram (Bohr's model) for a sodium atom (Na, Atomic No. = 11, Mass No. = 23). Show the distribution of protons, neutrons, and electrons.
2. Illustrate the formation of Magnesium Chloride (MgCl₂) through electron transfer.

View Answer Key – Section C

1. Sodium (Na): Nucleus contains 11 protons and 12 neutrons (23-11). Electrons are distributed in shells: K shell = 2, L shell = 8, M shell = 1. [Image of Bohr model of Sodium]
2. Magnesium Chloride (MgCl₂): One Mg atom (2, 8, 2) transfers one valence electron to each of the two Cl atoms (2, 8, 7). This forms one Mg²⁺ ion and two Cl^- ions, held by an electrovalent bond.

Section D – Short & Long Answer Questions

1. State the three main postulates of Bohr's atomic model.
2. Why do atoms form chemical bonds? Explain with reference to the octet rule.
3. What is valency? How is it determined from the electronic configuration of an element?

View Answer Key – Section D

1. Bohr's Postulates: (i) Electrons revolve around the nucleus in fixed circular paths called orbits or shells. (ii) Each shell has a definite energy level. (iii) An electron does not radiate energy as long as it stays in its orbit, but it can jump to a higher or lower orbit by absorbing or emitting a fixed amount of energy.
2. Reason for Bonding: Atoms form chemical bonds to achieve a stable electronic configuration, similar to that of the nearest noble gas. The octet rule states that atoms tend to gain, lose, or share electrons to have eight electrons in their outermost shell.
3. Valency: It is the combining capacity of an element. For metals with 1, 2, or 3 valence electrons, the valency is the number of valence electrons. For non-metals with 5, 6, or 7 valence electrons, the valency is calculated as (8 - number of valence electrons).

🔗 Related ICSE Class 9 Resources

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• 📘 ICSE Class 9 Chemistry Quiz – Atomic Structure MCQs Online
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📚 ICSE Class 9 Atomic Structure and Chemical Bonding Questions and Answer