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Quizzes > Science

Electron Configuration Quiz: Atomic Structure Practice

Quick atomic structure quiz to test your knowledge. Instant results.

Editorial: Review CompletedCreated By: Sheena GoldbergUpdated Aug 27, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art atoms and molecules near periodic table elements on teal background for atomic structure and bonding quiz

Use this electron configuration quiz to check how electrons fill orbitals and shape atomic structure, and to spot what to review before an exam. It covers subshell order, valence electrons, and common exceptions. For more practice, try our electron configuration test, work through electron configuration practice questions, and sharpen notation with an orbital notation quiz.

Which subatomic particle has a positive charge?
Electron
Neutron
Proton
Photon
Protons are positively charged particles found in the nucleus of an atom, whereas electrons are negatively charged and neutrons are neutral. The number of protons defines the atomic number and thus the identity of the element. Photons are particles of light and carry no electric charge.
The atomic number of an element is defined as the number of which particles in the nucleus?
Nucleons
Electrons
Protons
Neutrons
The atomic number corresponds to the number of protons in an atom's nucleus and uniquely identifies an element. Neutrons and electrons do not determine the atomic number. Nucleons refer collectively to protons and neutrons.
Isotopes of an element have the same atomic number but differ in what property?
Number of electrons
Number of protons
Number of neutrons
Atomic radius
Isotopes are atoms of the same element (same proton count) that differ in neutron count, leading to different mass numbers. The proton count remains constant across isotopes, and atomic radii differences are secondary effects. Electrons can change only when ions form, not isotopes.
The mass number of an atom equals the sum of which subatomic particles?
Protons and neutrons
Neutrons and electrons
Protons and electrons
Protons, neutrons, and electrons
Mass number is defined as the total number of protons and neutrons in the nucleus (also called nucleons). Electrons contribute negligible mass relative to nucleons and are not included. Including electrons would give the atomic mass of a neutral atom, not the mass number.
An ion is formed when an atom gains or loses which subatomic particle?
Protons
Photons
Electrons
Neutrons
An ion forms when an atom loses or gains electrons, resulting in a net positive or negative charge. Protons remain in the nucleus and are not gained or lost under chemical conditions. Neutrons are also in the nucleus and are unaffected. Photons are particles of light and are not involved.
Which element has the atomic number 6?
Oxygen
Boron
Nitrogen
Carbon
The atomic number 6 corresponds to carbon, meaning it has six protons in its nucleus. Nitrogen is atomic number 7 and oxygen is atomic number 8. Boron's atomic number is 5.
The average atomic mass of an element is based on the weighted average of its naturally occurring what?
Molecules
Ions
Isotopes
Allotropes
Average atomic mass is calculated by taking a weighted average of the masses of all naturally occurring isotopes of an element based on their relative abundances. Ions and molecules are not used in this calculation. Allotropes are different structural forms of the same element, not separate isotopes.
What is the ground-state electron configuration of an oxygen atom?
1s2 2s2 2p3 3s1
1s2 2s1 2p5
1s2 2s2 2p6
1s2 2s2 2p4
Oxygen has eight electrons. Following the Aufbau principle, the configuration fills 1s, 2s, then 2p orbitals, resulting in 1s2 2s2 2p4. The other configurations violate the order or electron count.
According to Hund's rule, electrons occupy degenerate orbitals by first filling them how?
In pairs with opposite spins
Only after lower orbitals are full
Singly with parallel spins
In the highest energy first
Hund's rule states that electrons fill degenerate orbitals singly and with parallel (same) spin before pairing up. This minimizes electron - electron repulsion and lowers energy. The rule applies after lower energy orbitals are filled according to the Aufbau principle.
What is the maximum number of electrons that can occupy the third principal energy level (n=3)?
6
10
18
8
The formula 2n2 gives the maximum electron capacity of a shell. For n=3, this is 2×3²=18 electrons distributed among 3s, 3p, and 3d orbitals. The other numbers represent subshell capacities or lower shells.
How many orbitals are present in a d subshell?
3
9
7
5
A d subshell corresponds to an angular momentum quantum number l=2, which has 2l+1=5 magnetic quantum number values, hence 5 orbitals. Each orbital can hold two electrons with opposite spins.
Which principle states that no two electrons in an atom can have the same four quantum numbers?
Aufbau principle
Pauli exclusion principle
Heisenberg uncertainty principle
Hund's rule
The Pauli exclusion principle dictates that each electron in an atom must have a unique set of quantum numbers (n, l, m_l, m_s). This explains electron pairing and the structure of the periodic table. The other principles address ordering of orbital filling or measurement limits.
Which orbital shape corresponds to a p orbital?
Cloverleaf
Spherical
Dumbbell-shaped
Toroidal
P orbitals have a characteristic dumbbell shape with two lobes on opposite sides of the nucleus. S orbitals are spherical, and some d orbitals have cloverleaf shapes. Toroidal shapes are uncommon in basic atomic orbitals.
Moving from left to right across a period in the periodic table, atomic radius generally how does it change?
Varies unpredictably
Remains constant
Decreases
Increases
Across a period, the nuclear charge increases while electrons are added to the same shell, pulling electrons closer to the nucleus and decreasing atomic radius. This trend is consistent across the s- and p-block elements.
Which of the following is not a quantum number used to describe an electron in an atom?
Magnetic quantum number
Charge quantum number
Spin quantum number
Principal quantum number
The four quantum numbers are principal (n), azimuthal or angular momentum (l), magnetic (m_l), and spin (m_s). There is no 'charge quantum number' since an electron's charge is a fixed constant. This set fully describes an electron's state in an atom.
How many radial nodes does a 3p orbital have?
0
1
2
3
The number of radial nodes in an orbital equals n?l?1. For a 3p orbital, n=3 and l=1, so 3?1?1=1 radial node. Radial nodes are spherical surfaces where the probability density is zero.
Which ion is isoelectronic with the noble gas Argon (Ar)?
S3?
K2+
Cl?
Ca+
Argon has 18 electrons. A chloride ion (Cl?) has 17 protons and one extra electron, giving it 18 electrons and making it isoelectronic with Ar. Ca+ (20?1=19), K2+ (19?2=17), and S3? (16+3=19) each have different electron counts.
Which series of the hydrogen emission spectrum lies entirely in the ultraviolet region?
Paschen
Brackett
Balmer
Lyman
The Lyman series involves electron transitions to the n=1 level and produces photons in the ultraviolet range. The Balmer series (n=2) is visible, the Paschen (n=3) is infrared, and Brackett (n=4) is deeper infrared.
In mass spectrometry, what is directly measured before calculating the mass-to-charge ratio (m/z) of ions?
Ionization energy
Light absorbance
Heat change
Degree of deflection in a magnetic field
Mass spectrometers measure how much ion beams are deflected in electric and magnetic fields; this deflection is then used to calculate the m/z value. Ionization energy is not directly measured, nor are light absorbance or heat change. The radius or angle of deflection is key in determining m/z.
Which phenomenon could not be explained by the Bohr model of the atom?
Discrete spectral lines of hydrogen
Ground state energy
Rydberg formula for energy levels
Fine structure of spectral lines
The Bohr model successfully explained hydrogen's discrete spectral lines and ground state energy, and it aligned with the Rydberg formula. However, it could not account for the fine structure (small splittings) observed in spectral lines, which requires relativistic and spin considerations.
For which of the following atoms is the 3d subshell being filled immediately after the 4s subshell in the ground-state electron configuration?
Calcium (Ca)
Potassium (K)
Scandium (Sc)
Argon (Ar)
Scandium (Z=21) has the electron configuration [Ar] 4s2 3d1, showing that after filling 4s, electrons enter 3d. Calcium (Z=20) ends at 4s2, potassium (Z=19) ends at 4s1, and argon (Z=18) has filled up to 3p6.
Among the following species, which has the largest atomic radius?
Ne
F?
O2?
Na+
Anions such as O2? have more electron - electron repulsion and thus a larger radius than their neutral or cation counterparts. F?, Ne, and Na+ all have ten electrons, but O2? has eight protons attracting ten electrons, leading to greater repulsion and an expanded radius.
Which fundamental equation describes the behavior of electrons in atoms using wavefunctions?
Einstein's mass - energy equivalence
Schrödinger equation
Planck's radiation law
Newton's second law
The Schrödinger equation is the core equation of quantum mechanics that yields wavefunctions for electrons in atoms, predicting energy levels and orbital shapes. Newton's laws apply to classical mechanics, and Einstein's and Planck's laws address relativity and radiation, respectively.
The fine-structure constant (?) is a dimensionless number characterizing the strength of electromagnetic interaction. What is its approximate value?
1/1000
1/16
1/12
1/137
The fine?structure constant ? ? 7.297×10?3, which is approximately 1/137. It combines fundamental constants (e, ?, c) to measure electromagnetic coupling. The other options are not dimensionless or correct approximations.
In Moseley's law, the relationship ?? = k(Z ? ?) describes the frequency of X-rays where ? is the screening constant. What does this screening constant represent?
Atomic mass isotope effect
Spin - orbit coupling
Effective inner-electron shielding
Ionization energy shift
In Moseley's law, ? accounts for the shielding of nuclear charge by inner electrons, reducing the effective nuclear charge felt by the electron involved in X-ray emission. It is not related to isotope effects, ionization energy shifts, or spin - orbit interactions.
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Study Outcomes

  1. Understand Atomic Components -

    Grasp the roles of protons, neutrons, and electrons as you tackle atomic structure quiz challenges and basic atomic structure questions.

  2. Determine Electron Configurations -

    Identify electron arrangements in shells and subshells to answer atomic structure questions accurately and predict element behavior.

  3. Analyze Periodic Trends -

    Examine periodic table quiz prompts to recognize patterns in atomic radius, electronegativity, and ionization energy across the periodic table.

  4. Apply Chemical Bonding Concepts -

    Use insights from the chemical bonding quiz to differentiate between ionic, covalent, and metallic bonds and their properties in compounds.

  5. Evaluate Element Properties -

    Assess element structure quiz items to correlate atomic number, mass number, and isotopes with real-world chemical characteristics.

  6. Explore Molecular Interactions -

    Connect atoms and molecules quiz insights to predict molecular geometry and bonding patterns in simple and complex molecules.

Cheat Sheet

  1. Atomic Number, Mass Number, and Isotopes -

    The atomic number (Z) equals the number of protons and defines the element, while mass number (A) sums protons and neutrons. Recognizing Z and A is essential for atomic structure questions, element structure quizzes, and every atomic structure quiz. For example, carbon-12 and carbon-14 share Z but differ in A, a basis for radiometric dating.

  2. Electron Configuration Principles -

    Use the Aufbau principle (fill lowest energy orbitals first), Pauli exclusion principle (two electrons max per orbital), and Hund's rule (maximize unpaired spins) to write electron configs accurately. For example, oxygen's 1s² 2s² 2p❴ notation is a staple on the atomic structure quiz, as outlined in MIT OpenCourseWare.

  3. Periodic Trends: Radius, Ionization Energy & Electronegativity -

    Across a period, atomic radius decreases while ionization energy and electronegativity increase, peaking at fluorine, and the opposite trend occurs down a group. These patterns are frequently tested on a periodic table quiz, and tools like the mnemonic "FONClBrISCH" help recall electronegativity order (ACS).

  4. Chemical Bonding Basics -

    Ionic bonds form via electron transfer (e.g., NaCl), covalent bonds via sharing (e.g., H₂), and metallic bonds via delocalized electrons; understanding these types is crucial for any chemical bonding quiz. Applying the octet rule clarifies bonding patterns and predicts molecular shapes, as described by the American Chemical Society.

  5. Stoichiometry & Molar Mass Calculations -

    Use molar mass (g/mol) and Avogadro's number (6.022×10²³ mol❻¹) to interconvert grams, moles, and particles (e.g., 18.02 g H₂O = 1 mole = 6.022×10²³ molecules). Mastery of these stoichiometry skills is essential for atoms and molecules quiz problems and general chemical calculations (Khan Academy).

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