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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- A. Neutrons in the nucleus
- B. Protons in the nucleus
- C. Protons and neutrons combined
- D. Electron shells
Explanation: The atomic number equals the number of protons in the nucleus and determines the identity of the element.
Correct answer: Protons in the nucleus- A. shape of orbital
- B. main energy level and distance from the nucleus
- C. orientation of the orbital in space
- D. direction of spin
Explanation: The principal quantum number sets the shell, and therefore the main energy level and the average distance of the electron from the…
Correct answer: main energy level and distance from the nucleus- A. Three
- B. Five
- C. Seven
- D. Nine
Explanation: For the d subshell l equals 2, so m runs from minus 2 to plus 2, giving five values and therefore five orbitals.
Correct answer: Five- A. n = 2, l = 1, m = 0
- B. n = 3, l = 2, m = -2
- C. n = 2, l = 2, m = 1
- D. n = 4, l = 0, m = 0
Explanation: The azimuthal quantum number l is restricted to values from 0 up to n minus 1, so with n equal to 2 the only allowed values of l are 0 and…
Correct answer: n = 2, l = 2, m = 1- A. 8
- B. 10
- C. 18
- D. 32
Explanation: The capacity of a shell is 2n squared, so for n equal to 3 that is 2 times 9, which is 18.
Correct answer: 18- A. spherical
- B. dumbbell shaped
- C. doughnut shaped
- D. tetrahedral
Explanation: A p orbital has two lobes on opposite sides of the nucleus with a node at the nucleus itself, giving the familiar dumbbell shape, and the…
Correct answer: dumbbell shaped- A. pair up in the first orbital before entering the next
- B. occupy separate orbitals with parallel spins before pairing
- C. occupy the orbital of highest energy first
- D. always pair with opposite spins immediately
Explanation: Electrons repel one another, so they spread across orbitals of equal energy singly and with parallel spins before any orbital takes a…
Correct answer: occupy separate orbitals with parallel spins before pairing- A. [Ar] 3d4 4s2
- B. [Ar] 3d5 4s1
- C. [Ar] 3d6 4s0
- D. [Ar] 3d3 4s3
Explanation: Chromium promotes one 4s electron into the 3d subshell because a half filled d5 configuration alongside a half filled 4s is more stable…
Correct answer: [Ar] 3d5 4s1- A. continuously in any amount
- B. in discrete packets whose energy is proportional to frequency
- C. only as heat
- D. in packets whose energy is proportional to wavelength
Explanation: Planck proposed that radiation is emitted in quanta of energy E equal to h times the frequency, where h is Planck's constant.
Correct answer: in discrete packets whose energy is proportional to frequency- A. n = 1
- B. n = 2
- C. n = 3
- D. n = 4
Explanation: The Balmer series arises from transitions ending at n equal to 2 and it is the only hydrogen series that falls in the visible region…
Correct answer: n = 2- A. electrons can have any energy value
- B. electron energies inside an atom are quantised
- C. the nucleus contains neutrons
- D. hydrogen atoms contain more than one electron
Explanation: A hot gas emits light only at particular wavelengths, producing separate bright lines instead of a continuous band, and each line…
Correct answer: electron energies inside an atom are quantised- A. the cathode of the discharge tube
- B. the residual gas atoms losing electrons in a discharge tube
- C. the radioactive decay of uranium
- D. the anode metal evaporating
Explanation: Goldstein observed that cathode rays travelling through a perforated cathode knocked electrons off the residual gas atoms, leaving…
Correct answer: the residual gas atoms losing electrons in a discharge tube- A. 4p
- B. 3d
- C. 4d
- D. 5s
Explanation: Orbitals fill in order of increasing n plus l, and where that sum ties the lower n goes first.
Correct answer: 3d- A. the shape of the orbital
- B. the main energy level and the average distance of the electron from the nucleus
- C. the orientation of the orbital in space
- D. the direction of electron spin
Explanation: The value of n fixes the shell, so a larger n means a higher energy and an electron held further out on average.
Correct answer: the main energy level and the average distance of the electron from the nucleus- A. 0 only
- B. 0 and 1
- C. 0, 1 and 2
- D. 1, 2 and 3
Explanation: The azimuthal quantum number runs from 0 up to n minus 1, so for the third shell it takes the values 0, 1 and 2, corresponding to the 3s…
Correct answer: 0, 1 and 2- A. 8
- B. 18
- C. 32
- D. 2
Explanation: Shell capacity is 2n squared, so for n equal to 3 the maximum is 2 multiplied by 9, that is 18, made up of 2 in 3s, 6 in 3p and 10 in 3d.
Correct answer: 18- A. 3
- B. 5
- C. 7
- D. 1
Explanation: The number of orbitals in a subshell is 2l plus 1, and for a d subshell l equals 2, giving five orbitals that together hold up to ten…
Correct answer: 5- A. the electron density is maximum
- B. the probability of finding the electron is zero
- C. the nucleus is located
- D. two orbitals overlap
Explanation: The wave function passes through zero at a node, so the electron is never found there, and the number of nodes increases with the…
Correct answer: the probability of finding the electron is zero- A. pair up in the lowest orbital first
- B. occupy separate orbitals singly with parallel spins before any pairing occurs
- C. always have opposite spins
- D. fill the highest energy orbital first
Explanation: Spreading out into empty orbitals minimises electron electron repulsion, so nitrogen's three 2p electrons occupy the three separate p…
Correct answer: occupy separate orbitals singly with parallel spins before any pairing occurs- A. no two electrons in an atom can have the same set of all four quantum numbers
- B. electrons always pair up
- C. orbitals fill in order of increasing energy
- D. electrons occupy the nucleus
Explanation: Because the first three quantum numbers define an orbital, the principle limits any orbital to two electrons, which must then differ in…
Correct answer: no two electrons in an atom can have the same set of all four quantum numbersAtomic Structure MCQs: common questions
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