Free Atomic Structure MCQs with Answers
922 Atomic Structure MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Atomic structure covers the discovery of the proton, Planck's quantum theory, hydrogen emission spectra and the evidence for quantized energy levels. You will use quantum numbers to describe orbitals, distinguish s, p, d and f orbital shapes, and write electronic configurations, including the correct order of electron filling.
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922 questions · page 18 of 47
- A. 10
- B. 15
- C. 20
- D. 25
Explanation: Possible Transitions: An electron in the 6th shell (n=6) can transition to any lower energy level.
Correct answer: 15342. What are the values of orbital quantum number (l) and magnetic quantum number (m) for p-subshell?
- A. l = 1, m = 0, +1, -1
- B. l = 0, m = 0
- C. l = 2, m = 0, +/-1, +/-2
- D. l = 3, m = 0, +/-1, +/-2, +/-3
Explanation: Orbital Quantum Number (l): The value of l determines the shape of the subshell.l = 0 corresponds to an s-subshell (spherical shape).l = 1…
Correct answer: l = 1, m = 0, +1, -1- A. r²
- B. 1/r
- C. √r
- D. 1/√r
Explanation: In Bohr's model, angular momentum (L) is proportional to the principal quantum number n (L ∝ n) and the radius (r) is proportional to n²…
Correct answer: √r- A. -me⁴/8ε₀ ²h²
- B. -me²/8ε₀ ²h²
- C. -me⁴/8ε₀h²
- D. -me⁴/8ε₀ ²h²n²
Explanation: The total energy of an electron in the nth orbit of a hydrogen atom is given by the formula E = -me⁴ / (8 ε₀² h² n²).
Correct answer: -me⁴/8ε₀ ²h²- A. 9/16. a₀
- B. 3a₀
- C. 1.5a₀
- D. 4a₀
Explanation: The Bohr radius is given by r ∝ n²/Z. The radius of the second orbit of H (n=2, Z=1 is proportional to 4).
Correct answer: 9/16. a₀- A. +6.8 eV
- B. +20.4 eV
- C. -6.8 eV
- D. +3.4 eV
Explanation: The total energy in the 1st excited state (n=2) is E₂ = -13.6 eV / 2² = -3.4 eV.
Correct answer: -6.8 eV- A. x/9
- B. x/3
- C. 3x
- D. 9x
Explanation: In Bohr's model, the velocity of an electron is inversely proportional to the principal quantum number (v ∝ 1/n) Therefore, if the speed…
Correct answer: x/3- A. 16πx
- B. 8πx
- C. 4πx
- D. 32πx
Explanation: The de Broglie wavelength in the nth orbit is given by λ = 2πr/n. The radius of the nth orbit is rₙ = r₁n².
Correct answer: 16πx- A. Z=2
- B. Z=3
- C. Z=4
- D. Z=5
Explanation: First, the energy of the X-ray is calculated as E = hc/λ ≈ 40.6 eV. The energy of the n=2 to n=1 transition is ΔE = 10.2 Z².
Correct answer: Z=2- A. One
- B. Two
- C. Three
- D. Infinite
Explanation: The number of radial nodes is given by the formula n - l - 1. For a 3p orbital, the principal quantum number n=3 and the azimuthal quantum…
Correct answer: One- A. (√3/2).ħ
- B. (1/2).ħ
- C. 0
- D. h
Explanation: The formula for spin angular momentum is √s(s+1.ħ), where s is the spin quantum number. For an electron, s = 1/2.
Correct answer: (√3/2).ħ- A. λ = λ₁ + λ₂
- B. 1/λ = 1/λ₁ + 1/λ₂
- C. λ = λ₁λ₂ / (λ₁ + λ₂)
- D. λ² = λ₁ ² + λ₂ ²
Explanation: By the law of conservation of energy, the energy of the absorbed photon must equal the sum of the energies of the emitted photons (E = E₁…
Correct answer: 1/λ = 1/λ₁ + 1/λ₂- A. 4×10⁻³ m/s
- B. 5.8×10⁻⁴ m/s
- C. 4×10⁻⁵ m/s
- D. 4×10⁻⁶ m/s
Explanation: According to Heisenberg's uncertainty principle, Δx·Δp ≥ h/4π. The uncertainty in position Δx is the length of the box (0.1 m).
Correct answer: 5.8×10⁻⁴ m/s- A. 12
- B. 15
- C. 5
- D. 22
Explanation: The maximum number of spectral lines emitted when an electron de-excites from state n to the ground state is given by the formula N =…
Correct answer: 15- A. 10 emission spectral lines will be seen
- B. The ionization energy needed is less than 2 eV
- C. The longest emitted wavelength is less than 10/R (R = Rydberg's constant)
- D. The electronic separation from the center of the nucleus is more than 6Å
Explanation: The radius of the orbit is calculated by r = a₀(n²/Z), where a₀ ≈ 0.529 Å.
Correct answer: The electronic separation from the center of the nucleus is more than 6Å- A. 7 or 8
- B. 11 or 12
- C. 5 or 6
- D. 10 or 11
Explanation: Cu²⁺ electron configuration: [Ar] 3d⁹ We count electrons for which (l + m = 0): s-orbitals (l = 0, m = 0): 1s² + 2s² + 3s² → 6 electrons…
Correct answer: 10 or 11- A. 1.1 Å
- B. 9.15 Å
- C. 5 Å
- D. 11 Å
Explanation: The binding energy of the 4th state of He⁺ is E = 13.6(Z²/n²) = 3.4 eV. The kinetic energy of the ejected electron is 3.4 - 1.4 = 2.0 eV.
Correct answer: 5 Å- A. Large-angle back-scattering of particles
- B. Majority of particles passing undeflected through the foil
- C. Very few particles getting absorbed
- D. Wave nature of electrons
Explanation: Rutherford's key observation was the back-scattering of a few massive α-particles, which revealed a small, dense, positive nucleus.
Correct answer: Large-angle back-scattering of particles359. A 1kW radio transmitter operates at a frequency of 880 kHz. How many quanta per second does it emit?
- A. A) 1.71x10²¹
- B. B) 1.71x10³⁰
- C. C) 6.02x10²³
- D. D) 2.85x10²⁶
Explanation: First, find the energy of a single quantum (photon) using E = hf. Then, divide the total power of the transmitter (1000 J/s).
Correct answer: B) 1.71x10³⁰- A. 2 : 1
- B. 1 : 1
- C. 1 : 2
- D. 1 : 4
Explanation: Let the charge of a proton be 'e' and its mass be 'm'. An αparticle has a charge of 2e and a mass of approximately 4m.
Correct answer: 2 : 1