Free Electronic Configuration MCQs with Answers
103 Electronic Configuration MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Electronic configuration describes how electrons occupy shells, subshells and orbitals around an atom. Questions use the Aufbau principle, Pauli exclusion principle and Hund's rule to write configurations, identify valence electrons, form ions and explain periodic trends, including common exceptions such as chromium and copper.
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21. Alkali and alkaline earth metals impart colours when heated over burner. It is due to______________?
- A. Smaller electronegativity of alkali metals
- B. Smaller ionic radius of these metals
- C. De-excitation of electrons from higher energy levels to low energy level
- D. Excitation of electrons from low energy levels to higher energy levels
Explanation: Heat excites electrons in metal atoms to higher energy levels, and the characteristic colour appears when those electrons return to lower…
Correct answer: De-excitation of electrons from higher energy levels to low energy level- A. Group II-A
- B. Group IV-A
- C. Group VII-A
- D. Group VI-A
Explanation: The configuration 1s2 2s2 2p2 contains four valence electrons, so the element is carbon, which belongs to Group IV-A, or Group 14.
Correct answer: Group IV-A- A. Ferromagnetic
- B. Paramagnetic
- C. Diamagnetism
- D. Both A & B
Explanation: An unpaired electron has a magnetic moment, so a molecule containing one or more unpaired electrons is attracted by an external magnetic…
Correct answer: Paramagnetic- A. Noble gases
- B. Alkali metals
- C. Coinage metals
- D. Gun metals
Explanation: Noble gases have completely filled outermost shells in their neutral atomic form, which gives them exceptional stability and low chemical…
Correct answer: Noble gases- A. Auf bau principle
- B. Hunds rule
- C. Paulis Exclusion principle
- D. All these
Explanation: Molecular orbitals are filled using all three rules: the Aufbau principle fills lower-energy orbitals first, the Pauli exclusion principle…
Correct answer: All these- A. 6X
- B. 7Y
- C. 9Z
- D. 13W
Explanation: The species represented by atomic number 7 has configuration 1s2 2s2 2p3, with three unpaired electrons in the three p orbitals.
Correct answer: 7Y- A. 7f
- B. 7s
- C. 7p
- D. 7d
Explanation: According to the Aufbau filling order, the 6d subshell is followed by the 7p subshell, so the next electron enters 7p after 6d is…
Correct answer: 7p- A. 7
- B. 10
- C. 12
- D. 16
Explanation: A p-subshell has three orbitals, so according to Hund's rule its maximum unpaired electrons occur at p3, as in nitrogen: 1s2 2s2 2p3.
Correct answer: 7- A. [Ar]4s2
- B. [Ar]4s1
- C. [Kr]5s1
- D. [He]2s1
Explanation: Potassium has atomic number 19, so after the argon core containing 18 electrons, its nineteenth electron enters the 4s subshell.
Correct answer: [Ar]4s1- A. [Ar]4s1
- B. [Ar]4s2
- C. [Ar]3d104s1
- D. [Ar]3d94s2
Explanation: Copper has atomic number 29 and adopts the especially stable configuration [Ar]3d10 4s1, with a completely filled 3d subshell.
Correct answer: [Ar]3d104s1- A. O2+2
- B. N2-2
- C. B2
- D. O2-2
Explanation: N2 has 10 valence electrons, and N2^2- has 12, so the two additional electrons enter antibonding pi* orbitals separately according to…
Correct answer: N2-2- A. F - Cl - Br
- B. Li+1 - Na+1 - K+1
- C. F - Ne - Na+
- D. H+ - H- - H
Explanation: F-, Ne, and Na+ each contain 10 electrons: F- has 9 + 1 electrons, Ne has 10, and Na+ has 11 - 1 electrons.
Correct answer: F - Ne - Na+- A. Electrons fill orbitals with parallel spins until all the orbitals of the same energy are half filled then they go into sub-shells with anti-parallel (opposite) spin.
- B. The electrons in the same atom cannot have the same four quantum numbers
- C. There is maximum of two electrons is an orbital.
- D. None
Explanation: Hund's rule states that electrons occupy orbitals of equal energy singly with parallel spins before pairing begins.
Correct answer: Electrons fill orbitals with parallel spins until all the orbitals of the same energy are half filled then they go into sub-shells with anti-parallel (opposite) spin.- A. 5
- B. 4
- C. 3
- D. 2
Explanation: In the conventional description of Dempster's mass spectrometer, the apparatus is divided into five zones or parts, including ionisation…
Correct answer: 5- A. properties which depend upon mass
- B. arrangement of electrons in orbitals
- C. chemical properties
- D. all of the above
Explanation: Isotopes have the same atomic number and therefore the same electron arrangement in neutral atoms, giving them almost identical chemical…
Correct answer: properties which depend upon mass- A. they possess different mass number
- B. they possess different physical properties
- C. they possess same chemical properties
- D. they possess different position in the periodic table
Explanation: Isotopes have different mass numbers because they contain different numbers of neutrons, and this can give different physical properties.
Correct answer: they possess different position in the periodic table- A. arsenic
- B. uranium
- C. iodine
- D. nickel
Explanation: A mono-isotopic element has only one naturally occurring isotope. Arsenic is mainly 75As and iodine is 127I, whereas uranium occurs…
Correct answer: uranium- A. Gas
- B. Liquid
- C. Volatile solid
- D. All
Explanation: A gas can enter the ionisation chamber directly, so it does not need to be vaporised first.
Correct answer: Gas- A. Same number of neutrons
- B. Same mass number
- C. Same physical properties
- D. Same chemical properties
Explanation: Isotopes have the same number of protons and, in neutral atoms, the same number and arrangement of electrons.
Correct answer: Same chemical properties- A. H+ H H-
- B. Li+ Na+ K+
- C. C1- Br- I
- D. F- Ne Na+
Explanation: Isoelectronic species have the same number of electrons. F- has 9 + 1 = 10 electrons, Ne has 10 electrons, and Na+ has 11 - 1 = 10…
Correct answer: F- Ne Na+