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 19 of 47
- A. 3, 2, -2, ½
- B. 3, 3, 1, -½
- C. 3, 2, 1, -½
- D. 3, 1, 1, -½
Explanation: The rules for quantum numbers state that the azimuthal quantum number (l) must be less than the principal quantum number (n).
Correct answer: 3, 3, 1, -½- A. [Ar]3d⁵4s¹
- B. [Ar]3d⁶4s⁰
- C. [Ar]3d⁵4s⁰
- D. [Ar]3d⁶4s²
Explanation: The configuration of a neutral Fe atom is [Ar]3d⁶4s². To form the Fe³⁺ ion, it loses three electrons.
Correct answer: [Ar]3d⁵4s⁰- A. n=2, l=1, m=0, s=+1/2
- B. n=4, l=3, m=1, s=+½
- C. n=5, l=3, m=2, s=+½
- D. n=3, l=2, m=3, s=+½
Explanation: The rules for quantum numbers state that the magnetic quantum number (m. can range from -l to +l.
Correct answer: n=3, l=2, m=3, s=+½364. If the speed of an electron in Bohr's first orbit of hydrogen is x, the speed in the nth orbit is:
- A. x/n
- B. n/x
- C. nx
- D. n² x
Explanation: According to Bohr's model, the speed of an electron in an orbit is inversely proportional to the principal quantum number (v ∝ 1/n).
Correct answer: x/n- A. 2, 0, 0, +1/2
- B. 3, 2, 1, +1/2
- C. 3, 0, 0, +1/2
- D. 3, 1, 2, +1/2
Explanation: The ground state of Ne is 1s²2s²2p⁶. To reach the second excited state, a 2p electron is promoted to the next available higher energy…
Correct answer: 3, 1, 2, +1/2- A. n=1 to n=3
- B. n=2 to n=3
- C. n=4 to n=6
- D. n=3 to n=4
Explanation: The frequency of an absorption line is proportional to the energy difference between the orbits (ΔE = hf).
Correct answer: n=4 to n=6- A. 3
- B. 6
- C. 9
- D. 12
Explanation: In the Bohr-de Broglie model, an electron can occupy an orbit only if the circumference of that orbit equals an integer multiple of the…
Correct answer: 3- A. 59 eV
- B. 81 eV
- C. 79 eV
- D. None of these
Explanation: The energy to remove the first electron (first ionization energy) is given as 24.6 eV.
Correct answer: 79 eV- A. √6 ħ
- B. √2 ħ
- C. √12 ħ
- D. √20 ħ
Explanation: The formula for orbital angular momentum is L = √l(l+1.ħ), where (l) is the azimuthal quantum number. For a d-electron, l=2.
Correct answer: √6 ħ- A. Cr³⁺ , Fe³⁺
- B. Fe³⁺ , Mn²⁺
- C. Fe³⁺ , Co³⁺
- D. Sc³⁺ , Cr³⁺
Explanation: First, write the configurations of the neutral atoms: Mn is [Ar]3d⁵4s² and Fe is [Ar]3d⁶4s².
Correct answer: Fe³⁺ , Mn²⁺- A. λ/3
- B. 3λ/4
- C. 4λ/3
- D. 3λ
Explanation: According to given conditions; hv = 2E - E → E = hc/λ Also, wavelength of photon when transition occurs, from 4E/3 level to E level →…
Correct answer: 3λ372. The electronic configuration of an element is 1s , 2s , 2p , 3s , 3p , 3d , 4s¹.This represents its:
- A. Excited state
- B. Ground state
- C. Cationic form
- D. Anionic form
Explanation: The electronic configuration 1s , 2s , 2p , 3s , 3p , 3d , 4s¹, belongs to ground state of the element chromium (Cr) which has atomic…
Correct answer: Ground state- A. Deflection towards anode
- B. Deflection perpendicular to electric field
- C. Deflection towards cathode
- D. Deflection downward in electric field
Explanation: Protons are positively charged particles which show deflection towards cathode in electric field.
Correct answer: Deflection towards cathode- A. They are positively charged particles
- B. They are negatively charged particles
- C. They are neutral radiations
- D. They consist of protons
Explanation: The deflection toward the positive plate shows that cathode rays carry negative charge (electrons)
Correct answer: They are negatively charged particles- A. Nucleus occupies most of the space
- B. Atom is mostly empty space
- C. Electrons are heavier than nucleus
- D. α-particles are neutral
Explanation: Since most α-particles pass undeflected, atoms are largely empty with a dense, small nucleus.
Correct answer: Atom is mostly empty space- A. n₄→n₃
- B. n₃→n₂
- C. n₂→n₁
- D. n₃→n₁
Explanation: The largest energy difference (n₃→n₁). gives the highestenergy photon (E = hν).
Correct answer: n₃→n₁- A. To n=1
- B. To n=2
- C. To n=3
- D. To n=4
Explanation: The Balmer series (transitions to n=2). lies in the visible region of the spectrum.
Correct answer: To n=2- A. Neutrons
- B. Alpha particles
- C. Canal rays
- D. Electrons
Explanation: Goldstein discovered canal rays (positive rays) traveling opposite to cathode rays.
Correct answer: Canal rays- A. n = 2 → n = 1
- B. n = 3 → n = 2
- C. n = 4 → n = 3
- D. n = 5 → n = 4
Explanation: Lyman series lies in the UV region transitions to n=1..
Correct answer: n = 2 → n = 1- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Nitrogen has 7 electrons. The first 2 fill the 1s orbital, next 2 fill the 2s orbital.
Correct answer: Option B