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Quizzes > Science

Quantum Numbers Quiz: Test Orbitals and Electron Configurations

Quick, free quantum numbers practice quiz with instant results.

Editorial: Review CompletedCreated By: Leago MathebulaUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper cutout style periodic table blocks, electrons orbiting nucleus, quiz theme art on coral background

Use this quantum numbers quiz to check your understanding of orbitals, electron configurations, and how they connect to periodic trends. Warm up with periodic table practice questions, try an elements practice quiz to review names and basics, or challenge yourself with a quick periodic table quiz before you start.

What is the atomic number of oxygen?
6
16
8
2
The atomic number of an element equals its number of protons. Oxygen has eight protons in its nucleus, so its atomic number is 8. This is the fundamental identifier for each element in the periodic table. More details can be found at .
Which element has the chemical symbol 'Na'?
Nobelium
Nitrogen
Nickel
Sodium
The symbol 'Na' comes from the Latin 'natrium' and represents sodium, which has atomic number 11 on the periodic table. It’s a soft, reactive alkali metal. See more at .
The periodic table is arranged in order of increasing what?
Boiling point
Electronegativity
Atomic number
Atomic mass
The modern periodic table is organized by increasing atomic number, which corresponds to the number of protons in an atom. This arrangement reveals periodic trends and chemical behavior. For more information visit .
How many electrons can occupy the second energy level (shell) in an atom?
18
2
4
8
The second shell corresponds to principal quantum number n=2, which can hold a maximum of 2n² = 8 electrons. These occupy the 2s and 2p subshells. More details are at .
Which of the following is a noble gas?
Chlorine
Oxygen
Argon
Bromine
Argon is in group 18 of the periodic table and is a noble gas, characterized by a full valence shell and low reactivity. Noble gases are stable because they have complete electron shells. Read more at .
Alkali metals are located in which group of the periodic table?
17
2
18
1
Alkali metals occupy group 1 and include elements like lithium, sodium, and potassium. They have a single valence electron and are highly reactive. See group details at .
What is the principal quantum number (n) for the valence shell of chlorine (Cl)?
3
2
5
4
Chlorine has the electron configuration [Ne]3s²3p?, so its valence electrons occupy the third shell where n=3. The principal quantum number indicates the shell level. More at .
The symbol 'Fe' represents which element?
Fermium
Iron
Francium
Fluorine
The chemical symbol 'Fe' comes from the Latin word 'ferrum,' meaning iron. Iron is element 26 on the periodic table. Learn more at .
Which element is located in period 3, group 16?
Chlorine
Phosphorus
Sulfur
Silicon
Period 3, group 16 corresponds to sulfur, with electron configuration [Ne]3s²3p?. It’s a nonmetal known for its role in proteins and fertilizers. More at .
What is the maximum number of electrons that can occupy a single p orbital?
2
1
6
3
Each orbital can hold up to two electrons with opposite spins according to the Pauli exclusion principle. A p orbital holds a maximum of two electrons. More explanation at .
Which rule states that electrons occupy degenerate orbitals singly before pairing?
Hund's rule
Heisenberg uncertainty principle
Pauli exclusion principle
Aufbau principle
Hund's rule dictates that electrons fill degenerate orbitals singly to maximize total spin before pairing. This minimizes electron-electron repulsions. See more at .
According to the Aufbau principle, which subshell is filled after 4s?
5s
4d
4p
3d
The Aufbau principle states that electrons occupy the lowest available energy orbitals first. After filling 4s, electrons enter the 3d subshell. More details at .
What is the electron configuration of magnesium (atomic number 12)?
1s² 2s² 2p? 3s²
1s² 2s² 2p? 3s¹
1s² 2s² 2p? 3p²
1s² 2s² 2p? 3s²
Magnesium has 12 electrons, which fill 1s, 2s, 2p, and then 3s orbitals in order: 1s²2s²2p?3s². See configuration details at .
Which element has the electron configuration [Ne] 3s¹?
Sodium
Aluminum
Silicon
Magnesium
[Ne]3s¹ corresponds to sodium (Na), which has atomic number 11. It has a single electron beyond the neon core in the 3s subshell. More at .
Which periodic trend increases across a period from left to right?
Atomic volume
Metallic character
Atomic radius
Electronegativity
Electronegativity generally increases across a period as atoms more strongly attract electrons due to increasing nuclear charge. Atomic radius and metallic character decrease. More at .
What does the Pauli exclusion principle state?
No two electrons in the same atom can have the same set of four quantum numbers
It is impossible to know exact position and momentum simultaneously
Electrons fill the lowest available energy orbitals first
Electrons occupy degenerate orbitals singly before pairing
The Pauli exclusion principle asserts that no two electrons in an atom can share all four quantum numbers, ensuring unique electron states. This underpins the structure of the periodic table. Read more at .
How many unpaired electrons are present in the ground state of carbon (C)?
4
1
2
3
Carbon has the configuration 1s²2s²2p²; the two 2p electrons occupy separate orbitals with parallel spins, giving two unpaired electrons. More details at .
Which element is the most electronegative on the periodic table?
Fluorine
Nitrogen
Chlorine
Oxygen
Fluorine has the highest electronegativity (3.98 on the Pauling scale) because of its small size and high effective nuclear charge. It strongly attracts bonding electrons. See more at .
Which statement best describes the trend in first ionization energy across a period?
It fluctuates randomly
It generally decreases from left to right
It generally increases from left to right
It remains constant across a period
First ionization energy generally increases across a period due to higher nuclear charge attracting electrons more strongly, making them harder to remove. Exceptions occur at subshell boundaries. Learn more at .
Which electron configuration represents the ground state of chromium (Cr, Z=24)?
[Ar] 3d4 4s2
[Ar] 3d5 4s1
[Ar] 3d10 4s2
[Ar] 3d6 4s0
Chromium attains extra stability by having a half-filled 3d subshell and a single 4s electron, so its configuration is [Ar]3d5 4s1. This anomaly arises from exchange energy. More at .
What is the effective nuclear charge (Zeff) experienced by a valence electron in sodium?
1
10
11
2
Zeff ? Z – S, where S is the shielding by inner electrons. For sodium (Z=11) with 10 core electrons, Zeff ? 11 – 10 = 1. This determines its chemical reactivity. See calculations at .
How many nodal planes does a 2p orbital have?
1
0
3
2
A 2p orbital has one nodal plane through the nucleus where the probability of finding an electron is zero. This divides the orbital into two lobes. More at .
Which quantum number describes the orientation of an orbital in space?
Spin quantum number (m?)
Principal quantum number (n)
Azimuthal quantum number (?)
Magnetic quantum number (m?)
The magnetic quantum number m? indicates the orientation of an orbital relative to an external magnetic field. Its values range from –? to +?. More information at .
How many unpaired electrons are in ground-state iron (Fe, Z=26)?
6
0
2
4
Iron has configuration [Ar]3d?4s². The 3d subshell holds six electrons, which occupy five orbitals with four unpaired and one paired, giving four unpaired electrons. More at .
Which element has the highest first ionization energy among these?
Neon
Helium
Lithium
Beryllium
Helium has the highest first ionization energy because its two electrons are tightly bound in the 1s orbital with minimal shielding. Neon is close but lower. See values at .
For a hydrogen-like atom, the energy of an electron depends only on which quantum number?
Principal quantum number (n)
Magnetic quantum number (m?)
Azimuthal quantum number (?)
Spin quantum number (m?)
In hydrogen-like atoms (single electron), energy levels depend solely on n because there are no electron-electron interactions. ?, m?, and m? only affect orbital shape and orientation. More at .
Identify the term for the shape of a d?y orbital.
Torus
Spherical
Cloverleaf
Dumbbell
Most d orbitals (including d?y) have a cloverleaf shape with four lobes lying between the axes. This arises from the angular part of the wavefunction. More at .
Which element commonly exhibits an oxidation state of +3?
Neon
Aluminum
Carbon
Calcium
Aluminum typically loses three electrons to achieve a full octet, giving it a +3 oxidation state in many compounds (e.g., Al?O?). See more at .
What is the trend in atomic radius down a group?
It decreases
It increases
It remains constant
It fluctuates randomly
Atomic radius increases down a group because each successive element has an additional electron shell, outweighing the increase in nuclear charge. More at .
Which set of quantum numbers corresponds to the last electron in nickel (Ni, Z=28)?
n=4, l=0, m?=0, m?=?½
n=3, l=0, m?=0, m?=+½
n=4, l=1, m?=0, m?=+½
n=3, l=2, m?=+2, m?=+½
Nickel’s configuration ends in 4s², so the last electron has n=4, l=0, m?=0, and is paired, giving m? = ?½. Quantum numbers uniquely identify that electron. More at .
Which element in its ground state has a half-filled p subshell?
Carbon
Fluorine
Nitrogen
Oxygen
Nitrogen has the electron configuration [He]2s²2p³, which gives exactly half-filled p orbitals with three unpaired electrons, a particularly stable arrangement. See more at .
According to the Rydberg formula, which constant determines the wavelengths of spectral lines in hydrogen?
Planck constant
Faraday constant
Rydberg constant
Bohr radius
The Rydberg constant (R?) appears in the formula 1/? = R? (1/n?² – 1/n?²) for hydrogen spectral lines. It quantifies the energy difference between levels. More at .
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Study Outcomes

  1. Understand Periodic Table and Quantum Numbers Fundamentals -

    Grasp how elements are arranged by atomic number and how quantum numbers define electron positions, solidifying your base for the periodic table and quantum numbers quiz.

  2. Analyze Atomic Structure -

    Break down the structure of atom quiz concepts by mapping electrons to shells and subshells, deepening your insight into atomic architecture.

  3. Identify Quantum Numbers -

    Determine the n, l, m, and s values for electrons in various orbitals, boosting your speed and accuracy in quantum numbers quiz questions.

  4. Apply Electron Configuration Rules -

    Use Aufbau, Pauli exclusion, and Hund's rules to write electron configurations, preparing you for advanced problems in the atomic structure quiz.

  5. Evaluate Periodic Trends -

    Assess trends such as atomic radius, ionization energy, and electronegativity to predict element behavior, strengthening your periodic table quiz performance.

  6. Differentiate Orbital Shapes -

    Recognize the shapes and energy levels of s, p, d, and f orbitals, enabling you to confidently tackle orbital-related questions in the quantum numbers quiz.

Cheat Sheet

  1. Periodic Trends Mastery -

    Understand how atomic radius decreases across a period and increases down a group due to effective nuclear charge and electron shielding (Chemistry LibreTexts). Recognize that ionization energy and electronegativity generally increase from left to right but decrease top to bottom, helping predict reactivity and bond types. Use the mnemonic "FONCl BrISCH" to recall the most electronegative elements (Fluorine, Oxygen, Nitrogen, Chlorine, Bromine, Iodine, Sulfur, Carbon, Hydrogen).

  2. Four Quantum Numbers -

    Review the principal (n), angular (l), magnetic (ml), and spin (ms) quantum numbers, which uniquely describe each electron's state (Atkins' Physical Chemistry). Remember that n defines energy level, l (0 to n - 1) defines subshell shape, ml ( - l to +l) defines orbital orientation, and ms (±½) defines spin. Practice by assigning quantum numbers to electrons in carbon's 2p orbital: n=2, l=1, ml= - 1,0,+1, ms=±½.

  3. Electron Configuration Rules -

    Apply the Aufbau principle, Pauli exclusion principle, and Hund's rule to build configurations from hydrogen onward (IUPAC Recommendations). For example, oxygen's configuration is 1s² 2s² 2p❴, filling each 2p orbital singly before pairing. A quick check: the sum of superscripts equals the atom's atomic number, ensuring accuracy.

  4. Orbital Shapes & Subshells -

    Visualize s (spherical), p (dumbbell), d (cloverleaf), and f (complex) orbitals to predict bonding angles and molecular geometry (University of California Chemistry). Sketch or use 3D models to see nodal planes and lobes. As a tip, link p-orbital lobes to "dumbbells" you might lift at the gym to remember their shape!

  5. Effective Nuclear Charge & Shielding -

    Calculate Zeff ≈ Z - S using Slater's rules to estimate how strongly an electron feels the nucleus (University of Oxford). Higher Zeff means smaller atomic radius and higher ionization energy. Compare elements in the same period to see how inner electrons shield outer ones differently.

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