Chapter 4: Structure of the Atom Application Questions | science Class 9 CBSE

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Chapter 4: Structure of the Atom Application Questions | science Class 9 CBSE | ByteNotes.in

Application Question

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Question 1

Applied Concept

Q1. Define atomic number and mass number with examples.

Atomic number (Z): Number of protons in an atom — e.g., H = 1.
Mass number (A): Sum of protons and neutrons — e.g., O = 16.
Z identifies the element.
A varies in isotopes of the same element.
Example: C has Z = 6 and A = 12.

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Question 2

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Q2. State any five features of Bohr’s atomic model.

Electrons revolve in fixed energy orbits.
Orbits are labeled as K, L, M... or n=1,2,3...
Electrons don’t radiate energy while in stable orbits.
Energy is absorbed/emitted when jumping between orbits.
Explains stability of atoms unlike Rutherford’s model.

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Question 3

Applied Concept

Q3. Define isotopes. Give two examples with uses.

Atoms of same element with same atomic number but different mass numbers.
Example 1: U-235 used in nuclear reactors.
Example 2: I-131 used in treating goitre.
They have identical chemical but different physical properties.
Used in medicine, agriculture, industry.

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Question 4

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Q4. What are the drawbacks of Rutherford’s model?

Couldn’t explain electron stability in circular orbits.
Revolving charges should emit radiation and lose energy.
Electrons would spiral into the nucleus.
Didn’t explain line spectra of atoms.
No explanation for energy quantization.

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Question 5

Applied Concept

Q5. Explain Bohr-Bury rules for electronic configuration.

1st shell (K) holds max 2 electrons, 2nd (L) = 8, and so on.
Maximum electrons in shell = 2n².
Shells filled in order of increasing energy.
Outer shell can have max 8 electrons.
New shell starts only after inner ones are filled.

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Question 6

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Q6. Calculate number of protons, electrons, and neutrons in Cl (Z=17, A=35).

Protons = 17 (Z).
Electrons = 17 (neutral atom).
Neutrons = 35 - 17 = 18.
Used to write atomic structure.
Confirms charge neutrality and isotopic form.

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Chapter 4: Structure of the Atom | Application Questions

Q1. Define atomic number and mass number with examples.

Q2. State any five features of Bohr’s atomic model.

Q3. Define isotopes. Give two examples with uses.

Q4. What are the drawbacks of Rutherford’s model?

Q5. Explain Bohr-Bury rules for electronic configuration.

Q6. Calculate number of protons, electrons, and neutrons in Cl (Z=17, A=35).

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