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Atomic Structure MCQs for MDCAT Practice

Chemistry section, Atomic Structure chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

The bank has 1,916 active questions on this chapter. Your first 500 practice attempts are free, and every attempt includes a worked explanation.

  1. Question 1
    The electronic configurations of the noble gases are:
    • ns2, np5
    • ns2, np6 (correct answer)
    • ns2, np4 , nd8
    • ns2, np5, nd10
    Correct answer: B
    Noble gases possess a stable, complete valence electron shell configuration, making them unreactive. This MCQ tests understanding of their characteristic electronic structure.
  2. Question 2
    The mass of one mole of electron is
    • 1.8 mg
    • 0.184mg
    • 0.54 mg (correct answer)
    • 64 mg
    Correct answer: C
    Calculate the mass of one mole of electrons using fundamental constants like Avogadro's number and the electron's charge.
  3. Question 3
    Elements in the same vertical group of the periodic table have same
    • Number of electrons
    • Atomic number
    • Number of valence electrons (correct answer)
    • Electronic configurations
    Correct answer: C
    Elements in the same group share similar chemical properties due to having the same number of valence electrons, dictating their reactivity.
  4. Question 4
    Which of the following series of elements is listed in order of increasing atomic radius?
    • Na, Mg, Al, Si
    • C, N O, F
    • I, Br, Cl, F
    • O, S, Se, Te (correct answer)
    Correct answer: D
    Atomic radius generally increases down a group and decreases across a period due to changes in electron shielding and effective nuclear charge.
  5. Question 5
    which rule violated in following configuration 1s2 2s2 2p6 3s2 3p6 4s3
    • Aufbau (correct answer)
    • N+L rule
    • Hund's rule
    • Pauli's exclusion principle
    Correct answer: A
    The electron configuration 1s²2s²2p⁶3s²3p⁶4s³ violates the Aufbau principle because the 4s subshell cannot hold three electrons.
  6. Question 6
    Consider the element with atomic number 24. If we strictly followed the (n+l) rule without considering orbital stability, the outer electronic configuration would be:
    • 3d5 4s1
    • 3d4 4s2 (correct answer)
    • 3d6 4s0
    • 4s2 3d4
    Correct answer: B
    Test application of the (n+l) rule for predicting electron filling order in orbitals, disregarding half-filled/fully-filled orbital stability exceptions.
  7. Question 7
    The radius of the third Bohr orbit is:
    • 0.529 Å
    • 0.529 / 4 Å
    • 0.529 x 2 Å
    • 0.529 x 32 Å (correct answer)
    Correct answer: D
    The Bohr model dictates that the radius of an electron's orbit is directly proportional to the square of the principal quantum number (n²). Calculate the radius of the third orbit using this relationship.
  8. Question 8
    Which light colour has the longest wavelength?
    • Violet
    • Blue
    • Red (correct answer)
    • Green
    • Yellow
    Correct answer: C
    Understanding the electromagnetic spectrum reveals that red light possesses the longest wavelength, distinguishing it from other visible colors.

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Read the full Atomic Structure chapter notes: Atomic Structure notes. Or browse every chapter.