Structure of Atom — Class 11 Chemistry NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 11 Chemistry chapter "Structure of Atom" — 8 important questions with detailed answers for CBSE board exam preparation.
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TL;DR: Free step-by-step NCERT solutions for Class 11 Chemistry chapter "Structure of Atom" — 8 important questions with detailed answers for CBSE board exam…
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Key Questions Covered:
- An atom of element X has 12 protons and 14 neutrons. Write its atomic notatio…
- What are isotopes? Give an example and explain why they have similar chemical…
- Describe the Bohr model of the atom and state its limitations.
- What is the maximum number of electrons that can be accommodated in the M she…
- Explain the dual nature of electrons and how it relates to the quantum mechan…
- Calculate the de Broglie wavelength of a neutron moving at 3 × 10⁵ m/s. (Mass…
- + 2 more questions in the full chapter
Solutions Summary:
| Question | Status |
|---|---|
| An atom of element X has 12 protons and 14 neutrons. Writ… | ✓ Solved |
| What are isotopes? Give an example and explain why they h… | ✓ Solved |
| Describe the Bohr model of the atom and state its limitat… | ✓ Solved |
| What is the maximum number of electrons that can be accom… | ✓ Solved |
| Explain the dual nature of electrons and how it relates t… | ✓ Solved |
| Calculate the de Broglie wavelength of a neutron moving a… | ✓ Solved |
Showing 6 of 8 questions
Q1: An atom of element X has 12 protons and 14 neutrons. Write its atomic notation and identify the element.
Given:
Number of protons = 12
Number of neutrons = 14
Step 1: Determine atomic number.
Atomic number (Z) = Number of protons = 12
Step 2: Determine mass number.
Mass number (A) = Number of protons + Number of neutrons
Mass number (A) = 12 + 14 = 26
Step 3: Identify the element.
An atom with 12 protons is Magnesium (Mg).
Step 4: Write the atomic notation.
Atomic notation: ²⁶Mg₁₂ or Mg-26
Answer: The element is Magnesium (Mg), and its atomic notation is ²⁶Mg₁₂.
Q2: What are isotopes? Give an example and explain why they have similar chemical properties but different physical properties.
Definition of Isotopes:
Isotopes are atoms of the same element that have the same atomic number (same number of protons) but different mass numbers (different number of neutrons).
Example:
Carbon has three naturally occurring isotopes:
1. ¹²C (6 protons, 6 neutrons) — most abundant
2. ¹³C (6 protons, 7 neutrons) — less abundant
3. ¹⁴C (6 protons, 8 neutrons) — radioactive, used in dating
Why similar chemical properties?
→ Chemical properties depend on the electron configuration and number of v...
Q3: Describe the Bohr model of the atom and state its limitations.
Bohr Model of the Atom:
The Bohr model (1913) proposed that:
1. Electrons revolve around the nucleus in fixed circular orbits (called shells or energy levels).
2. Each orbit has a specific fixed energy, and electrons in an orbit do not radiate energy.
3. Electrons can jump between orbits by absorbing or emitting energy (photons) in fixed amounts.
4. The closer the orbit to the nucleus, the lower the energy of the electron.
Orbits are labeled as: K (n=1), L (n=2), M (n=3), etc.
Successes of Bo...
Q4: What is the maximum number of electrons that can be accommodated in the M shell? Also calculate the number of electrons in a neutral atom of Aluminum (Al, Z = 13).
Part 1: Maximum electrons in the M shell.
Using the formula: Maximum electrons = 2n²
where n = shell number
For M shell: n = 3
Maximum electrons = 2 × (3)² = 2 × 9 = 18 electrons
Answer: The M shell can accommodate a maximum of 18 electrons.
Part 2: Electron configuration of Aluminum (Z = 13).
Since Al has 13 protons, a neutral Al atom has 13 electrons.
Electron configuration (using shell notation):
K shell (n=1): 2 electrons (max = 2)
L shell (n=2): 8 electrons (max = 8)
M shell (n=3): 3 el...
Q5: Explain the dual nature of electrons and how it relates to the quantum mechanical model of the atom.
Dual Nature of Electrons:
Electrons exhibit both wave and particle properties, depending on how they are observed.
1. Particle Nature (Corpuscular):
→ Electrons have mass and charge
→ They can collide with other particles
→ They carry momentum (p = mv)
→ Demonstrated by the cathode ray experiment
2. Wave Nature:
→ Electrons can be diffracted and show interference patterns
→ They have a wavelength given by de Broglie's equation:
λ = h / p = h / (mv)
where h = Planck's co...
Q6: Calculate the de Broglie wavelength of a neutron moving at 3 × 10⁵ m/s. (Mass of neutron = 1.675 × 10⁻²⁷ kg, h = 6.626 × 10⁻³⁴ J·s)
De Broglie wavelength formula:
λ = h / (m × v) = h / p
where:
h = Planck's constant = 6.626 × 10⁻³⁴ J·s
m = mass of neutron = 1.675 × 10⁻²⁷ kg
v = velocity = 3 × 10⁵ m/s
Step 1: Calculate momentum (p).
p = m × v
p = 1.675 × 10⁻²⁷ kg × 3 × 10⁵ m/s
p = 5.025 × 10⁻²² kg·m/s
Step 2: Calculate de Broglie wavelength.
λ = h / p
λ = (6.626 × 10⁻³⁴ J·s) / (5.025 × 10⁻²² kg·m/s)
λ = 1.32 × 10⁻¹² m
λ = 1.32 pm (picometers)
Answer: The de Broglie wavelength of the neutron is 1.32 × 10⁻¹² m or 1.32 pm.
Showing 6 of 8 questions. Visit the full page for complete solutions.
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