Atomic Structure

Atomic Structure MDCAT MCQs with answers

84 past paper MCQs from Chemistry unit 2, Atomic Structure, across 6 topics. They are arranged topic by topic; bigger topics show a sample here and link to their full set and to study notes. Tap “Show answer” for the correct option and a short solution.

Practise as a quiz

Discovery of the Proton

1.The lightest positive rays are obtained from: (MDCAT 2020)

  1. hydrogen gas
  2. helium
  3. neon
  4. air
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Correct answer: (a) hydrogen gas

The positive ray is an ion of the gas in the tube, and the hydrogen ion is the lightest there is.

2.Which gas in a discharge tube produces the lightest canal ray particles? (MDCAT 2022)

  1. Ar
  2. He
  3. $\mathrm{H_2}$
  4. Ne
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Correct answer: (c) $\mathrm{H_2}$

The positive rays are ions of the gas, and the hydrogen ion, the proton, is the lightest of them.

3.How much heavier is the H-atom as compared to electron? (NUMS MDCAT 2025)

  1. 1937
  2. 1737
  3. 1837
  4. 1637
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Correct answer: (c) 1837

A hydrogen atom is about 1837 times as massive as an electron.

All 11 Discovery of the Proton MCQs → Discovery of the Proton notes →

Planck's Quantum Theory

4.The amount of energy associated with a quantum of radiation is directly proportional to its: (MDCAT 2020)

  1. photon
  2. wavelength
  3. frequency
  4. velocity
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Correct answer: (c) frequency

$E=h

5.According to Planck's quantum theory, if the frequency of photon is doubled, the value of hf will be: (KMU MDCAT 2025)

  1. Doubled
  2. Increased 3 times
  3. Increased 4 times
  4. Unchanged
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Correct answer: (a) Doubled

The energy of a quantum is $hf$, which is proportional to the frequency.

6.Highest energy for one quantum among radiation is: (SZABMU MDCAT 2025)

  1. microwave
  2. infrared
  3. ultra violet
  4. visible
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Correct answer: (c) ultra violet

Energy is $hf$, and of these four the ultraviolet has the highest frequency.

All 6 Planck's Quantum Theory MCQs → Planck's Quantum Theory notes →

Quantum Numbers and Orbitals

7.The maximum number of electrons that can be placed in one orbital is: (MDCAT 2020)

  1. 1
  2. 2
  3. 3
  4. 4
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Correct answer: (b) 2

The Pauli exclusion principle allows two electrons of opposite spin in one orbital.

8.According to which scientist is the probability of finding an electron at a certain position possible? (MDCAT 2022)

  1. Bohr
  2. de Broglie
  3. Hund
  4. Schrodinger
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Correct answer: (d) Schrodinger

The square of the wave function of the Schrodinger equation gives the probability of finding the electron in a region, which is what an orbital is.

9.Which set of quantum numbers is not allowed for an electron. (UHS MDCAT 2025)

  1. n=2, l=1, m=0, s=+1/2
  2. n=3, l=0, m=0, s=-1/2
  3. n=2, l=2, m=+1, s=+1/2
  4. n=1, l=0, m=0, s=+1/2
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Correct answer: (c) n=2, l=2, m=+1, s=+1/2

The azimuthal quantum number cannot reach the principal one, so $l=2$ is impossible when $n=2$.

All 26 Quantum Numbers and Orbitals MCQs → Quantum Numbers and Orbitals notes →

Shapes of Orbitals

10.The p orbital has: (MDCAT 2024)

  1. 2 lobes
  2. 3 lobes
  3. 4 lobes
  4. 5 lobes
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Correct answer: (a) 2 lobes

A p orbital is dumb-bell shaped, with two lobes on either side of the nucleus.

11.The maximum probability of finding an electron is at a distance of: (SIBA MDCAT 2025)

  1. 0.53 nm
  2. 0.35 nm
  3. 0.053 nm
  4. 0.0053 nm
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Correct answer: (c) 0.053 nm

The most probable distance of the electron of a hydrogen atom is the Bohr radius, $0.053\,\mathrm{nm}$.

12.Which atom has at least single electron in dumbell shape orbital? (SIBA MDCAT 2025)

  1. H
  2. He
  3. Li
  4. B
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Correct answer: (d) B

The p orbital is dumb-bell shaped, and boron is the first of these with an electron in one.

All 9 Shapes of Orbitals MCQs → Shapes of Orbitals notes →

Electronic Configuration

13.Which of the following orbitals will be filled before $4p$? (MDCAT 2020)

  1. $4s$
  2. $2p$
  3. $3d$
  4. $5s$
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Correct answer: (c) $3d$

By the $(n+l)$ rule the order runs $4s$, $3d$, $4p$, so $3d$ fills first of these.

14.Which element has the ground state electronic configuration $1s^2\,2s^2\,2p^6\,3s^2\,3p^6$? (MDCAT 2022)

  1. Ar
  2. O
  3. Na
  4. S
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Correct answer: (a) Ar

Eighteen electrons filling up to $3p$ is argon.

15.When the $6d$ orbital is filled, the entering electron goes into: (MDCAT 2023)

  1. $7s$
  2. $7p$
  3. $8s$
  4. $5f$
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Correct answer: (b) $7p$

By the $(n+l)$ rule the next lowest set after $6d$ is $7p$.

All 30 Electronic Configuration MCQs → Electronic Configuration notes →

Spectrum of Hydrogen

16.The splitting of spectral lines in magnetic field is (KMU MDCAT 2024)

  1. Aufbau principle
  2. Pauli exclusion principle
  3. Stark effect
  4. Zeeman effect
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Correct answer: (d) Zeeman effect

Splitting of spectral lines in a magnetic field is the Zeeman effect; in an electric field it is the Stark effect.

17.An element or its compound is first _____________ to get its ______________ spectrum by a spectrometer. (PMC Practice 2021)

  1. Freezed, continuous
  2. Freezed, line
  3. Volatilized, line
  4. Volatilized, continuous
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Correct answer: (c) Volatilized, line

The sample is vaporized so that its free atoms give the line spectrum by which it is identified.

Spectrum of Hydrogen notes →

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