How much energy is emitted when the electron of a hydrogen atom falls from n = 2 to n = 1 (Eₙ = −13.6/n² eV)?
Correct answer B. 10.2 eV
Topic / 39 questions
Atomic Structure MCQs
Atomic Structure MCQs are multiple-choice questions on the discovery of the proton, Planck's quantum theory, quantum numbers, orbitals and the rules for writing electronic configurations. They follow the MDCAT chemistry curriculum, and every question on MCQs360 shows its correct answer instantly so you can check your understanding as you go.
- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
What is the energy of the electron in the n = 3 orbit of a hydrogen atom (Eₙ = −13.6/n² eV)?
Correct answer D. −1.51 eV
Which configuration correctly represents a ground-state copper atom (Z = 29), an exception to the Aufbau order?
Correct answer C. [Ar] 3d¹⁰ 4s¹
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According to Hund’s rule, how are the three 2p electrons of a nitrogen atom arranged?
Correct answer C. One in each 2p orbital with parallel spins
The Paschen series of hydrogen is produced when electrons fall to which energy level?
Correct answer C. n = 3
In which region of the electromagnetic spectrum do the lines of the Lyman series of hydrogen lie?
Correct answer B. Ultraviolet
How are the lobes of the dxy orbital oriented?
Correct answer D. Between the x and y axes
What values can the azimuthal quantum number l have when n = 3?
Correct answer A. 0, 1, 2
Unlike that of cathode rays, the e/m value of positive rays ____
Correct answer C. depends on the gas present in the discharge tube
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Which scientist gave the name proton to the lightest positive particle obtained from hydrogen?
Correct answer D. Ernest Rutherford
If the wavelength of a photon is doubled, what happens to its energy?
Correct answer C. It is halved
Light of wavelength 663 nm has photons of energy 3.0 × 10⁻¹⁹ J. About how many such photons carry a total energy of 1.0 J?
Correct answer D. 3.3 × 10¹⁸
The wave number of a radiation is defined as ____
Correct answer B. the number of waves per unit length, equal to 1/λ
How many values of the magnetic quantum number m are possible when l = 2?
Correct answer C. 5
What is the maximum number of electrons that can have the quantum numbers n = 3 and l = 1?
Correct answer C. 6
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Using the (n + l) rule, which subshell is filled immediately after 4p?
Correct answer C. 5s
What is the electronic configuration of the Fe³⁺ ion (Z of Fe = 26)?
Correct answer C. [Ar] 3d⁵
What is the ground-state electronic configuration of chromium (Z = 24)?
Correct answer D. [Ar] 3d⁵ 4s¹
How many unpaired electrons are present in a ground-state iron atom (Z = 26)?
Correct answer D. 4
Which statement expresses Pauli’s exclusion principle?
Correct answer A. No two electrons in an atom can have the same set of four quantum numbers
About Atomic Structure MCQs
The first group of questions deals with discharge tube experiments: how canal (positive) rays are produced, why their e/m value depends on the gas in the tube and why they are deflected less than cathode rays. Planck's quantum theory follows, with short calculations of photon energy from E = hν and links to the line spectrum of hydrogen, where each line comes from an electron moving between energy levels.
Most of the remaining questions test quantum numbers and orbitals: allowed sets of n, l, m and s, the number of orbitals and electrons in a shell, and the shapes of s, p and d orbitals. You will also apply the Aufbau principle, the (n + l) rule, Pauli's exclusion principle and Hund's rule to write configurations and count unpaired electrons, including the exceptions chromium and copper.
Key facts to remember
- Canal (positive) rays were first observed by Eugen Goldstein in 1886; their e/m value is greatest when the discharge tube contains hydrogen.
- Planck's quantum theory states that energy is emitted or absorbed in discrete packets (quanta), with E = hν and h = 6.63 × 10⁻³⁴ J s.
- A proton is about 1836 times heavier than an electron.
- A shell with principal quantum number n has n² orbitals and can hold a maximum of 2n² electrons.
- The azimuthal quantum number l (0 to n − 1) fixes the shape of an orbital, and the magnetic quantum number m takes values from −l to +l.
- Chromium is [Ar]3d⁵4s¹ and copper is [Ar]3d¹⁰4s¹ because half-filled and completely filled d subshells are extra stable.
Exams that include Atomic Structure MCQs
Pakistan
- MDCAT
- ECAT
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Atomic Structure MCQs
- Memorise the order of filling (1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s) and check it with the (n + l) rule.
- Practise writing configurations for Z = 1 to 30, paying special attention to chromium and copper.
- For quantum number questions, test each option against l ≤ n − 1 and |m| ≤ l before choosing.
- Keep E = hν and c = νλ together in your notes, and convert units carefully in photon energy questions.
Frequently asked questions
What does the MDCAT syllabus include in Atomic Structure?
The PMDC MDCAT curriculum covers the discovery and properties of the proton through positive rays, Planck's quantum theory and photons, quantum numbers, shells, subshells and orbitals, the shapes of s, p and d orbitals, the hydrogen spectrum and electronic configuration using the Aufbau principle, Pauli's principle and Hund's rule.
Which exams ask Atomic Structure MCQs?
Atomic Structure is tested in MDCAT, ECAT, NUMS and AKU entry tests and in FSc board papers in Pakistan. It is also a core chapter for NEET and JEE Main in India and for HSC and medical admission tests in Bangladesh.
What is Hund's rule?
Hund's rule states that electrons entering a set of orbitals of equal energy, such as the three 2p orbitals, occupy them singly with parallel spins before any pairing takes place. This is why nitrogen has three unpaired electrons in its 2p subshell.
Last reviewed October 2026