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OAE Chemistry practice questions

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Question 1Nature of Science

A student measures the mass of a sample three times and obtains 5.02 g, 5.01 g, and 5.03 g, while the accepted value is 5.50 g. Which description best characterizes these measurements?

  1. Neither accurate nor precise
  2. Precise but not accurate Correct answer.
  3. Both accurate and precise
  4. Accurate but not precise

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to how close a measurement is to the accepted or true value. The three trials cluster tightly together (high precision) but all lie far from 5.50 g (low accuracy).

Question 2Nature of Science

In the scientific method, a hypothesis is best described as which of the following?

  1. A broad unifying principle supported by extensive evidence
  2. A testable, falsifiable proposed explanation for an observation Correct answer.
  3. A personal opinion that requires no evidence
  4. A final conclusion that cannot be revised

Explanation

A hypothesis is a tentative, testable statement that can be supported or refuted by experiment or observation. Falsifiability is the key feature that distinguishes a scientific hypothesis from an untestable claim.

Question 3Nature of Science

A chemist records a volume as 25.0 mL using a graduated cylinder marked in 1 mL increments. How many significant figures does this measurement have?

  1. Two
  2. Four
  3. Three Correct answer.
  4. One

Explanation

The digits 2 and 5 are certain, and the trailing zero after the decimal point is an estimated digit, so all three digits are significant. A measurement recorded with one estimated decimal place generally carries that many significant figures.

Question 4Nature of Science

Which statement best distinguishes a scientific law from a scientific theory?

  1. A law applies only to physics, while a theory applies only to biology
  2. A theory is a law that has not yet been tested
  3. A law is proven true, while a theory remains an unproven guess
  4. A law describes a consistent relationship, while a theory explains why that relationship occurs Correct answer.

Explanation

A scientific law typically states a consistent, often mathematical relationship observed in nature, whereas a theory is a well-substantiated explanatory framework for observations. Both are supported by evidence and neither is a mere guess.

Question 5Nature of Science

A researcher wants to determine whether a new fertilizer increases plant growth. Which design best controls for confounding variables?

  1. Randomly assign identical plants to fertilized and unfertilized groups kept under the same conditions Correct answer.
  2. Measure the growth of a single plant before and after applying fertilizer
  3. Give the fertilizer to plants in one greenhouse and compare them with untreated plants in a different greenhouse
  4. Give the fertilizer to all plants and measure growth over time

Explanation

A controlled experiment compares a treatment group with a control group while holding other variables constant, and random assignment reduces bias. Keeping both groups under identical conditions isolates the fertilizer as the only difference.

Question 6Nature of Science

A sample's mass is reported as 0.00450 kg. How many significant figures are present?

  1. Five
  2. Two
  3. Three Correct answer.
  4. Six

Explanation

Leading zeros before the first nonzero digit are not significant, but the trailing zero after the 5 is significant because it follows a decimal point. Thus 4, 5, and the final 0 are significant, giving three.

Question 7Nature of Science

Which practice most directly reflects the peer-review process in chemistry research?

  1. Removing data points that do not support the hypothesis
  2. Repeating an experiment until the desired result is obtained
  3. Publishing results immediately on a personal website without evaluation
  4. Having independent experts evaluate the methods and conclusions before publication Correct answer.

Explanation

Peer review involves independent qualified experts assessing the rigor, validity, and significance of a study before it is published. This scrutiny helps ensure that methods and conclusions meet scientific standards.

Question 8Nature of Science

A measurement is reported as 12.34 g with an uncertainty of ±0.02 g. Which statement about this measurement is correct?

  1. The uncertainty means the measurement is invalid
  2. The true value lies somewhere within a range around 12.34 g Correct answer.
  3. The measurement has only two significant figures
  4. The true value is exactly 12.34 g

Explanation

An uncertainty of ±0.02 g indicates that the reported value is an estimate within a range, so the true value is expected to fall near 12.34 g within that interval. All measurements carry some uncertainty and are never exact.

Question 9Nature of Science

Which of the following is an example of a qualitative observation rather than a quantitative one?

  1. The solution has a mass of 50.2 g
  2. The solution's volume is 25.0 mL
  3. The solution turns from clear to deep blue Correct answer.
  4. The solution's temperature is 298 K

Explanation

Qualitative observations describe properties such as color, odor, or texture without numerical measurement. A color change from clear to blue is descriptive, whereas masses, temperatures, and volumes are numerical.

Question 10Nature of Science

A student converts 3.75 cm to millimeters and reports 37.5 mm. Which principle justifies keeping three significant figures in the result?

  1. All conversions require rounding to one significant figure
  2. Addition and subtraction results are limited by the least precise decimal place
  3. Multiplication and division results keep the same number of significant figures as the least precise factor Correct answer.
  4. Trailing zeros are never significant in metric conversions

Explanation

When multiplying or dividing, the result carries the same number of significant figures as the measurement with the fewest significant figures. The conversion factor 10 mm/cm is exact, so the three significant figures of 3.75 cm are preserved.

Question 11Nature of Science

Which statement best describes the role of a control group in a chemistry experiment?

  1. It provides a baseline for comparison by lacking the variable being tested Correct answer.
  2. It receives the experimental treatment to maximize the effect
  3. It guarantees that the hypothesis is correct
  4. It eliminates the need for repeated trials

Explanation

A control group is held under the same conditions as the experimental group but does not receive the treatment, providing a baseline against which the effect of the variable can be measured. This comparison is essential for attributing observed changes to the tested variable.

Question 12Nature of Science

A chemist reports a result with four significant figures but the raw data support only two. Which issue does this most directly illustrate?

  1. Proper use of uncertainty propagation
  2. Failure to use a control group
  3. Overstating precision in reported results Correct answer.
  4. Incorrect identification of the independent variable

Explanation

Reporting more significant figures than the data justify overstates the precision of a measurement. Results should be rounded to reflect the actual certainty supported by the raw data.

Question 13Nature of Science

Which of the following best represents a scientific model in chemistry?

  1. A law that has been disproven
  2. A simplified representation used to explain and predict observations Correct answer.
  3. A permanent, unchanging representation of reality
  4. A guess made without any supporting evidence

Explanation

Scientific models are simplified representations, such as the Bohr or quantum mechanical model of the atom, that help explain and predict phenomena. Models are refined or replaced as new evidence emerges.

Question 14Nature of Science

A student claims a result is valid because it was obtained with a digital balance reading to 0.0001 g. Which reasoning flaw does this claim most likely reflect?

  1. Confusing high instrumental resolution with overall measurement accuracy Correct answer.
  2. Appropriately using a qualitative observation
  3. Properly identifying a controlled variable
  4. Correctly applying uncertainty propagation

Explanation

A balance reading to 0.0001 g has fine resolution, but accuracy also depends on calibration, technique, and systematic errors. Assuming that fine resolution guarantees an accurate or valid result confuses precision of the instrument with overall measurement quality.

Question 15Nature of Science

Which sequence correctly orders the general steps of a scientific investigation?

  1. Observation, hypothesis, experiment, conclusion Correct answer.
  2. Experiment, observation, conclusion, hypothesis
  3. Conclusion, hypothesis, observation, experiment
  4. Hypothesis, conclusion, observation, experiment

Explanation

Scientific inquiry typically begins with an observation that raises a question, followed by a testable hypothesis, an experiment to test it, and a conclusion drawn from the data. This logical order allows evidence to evaluate the hypothesis.

Question 16Nature of Science

In an experiment testing how temperature affects reaction rate, which is the independent variable?

  1. The volume of reactants
  2. The reaction rate
  3. The time to completion
  4. The temperature Correct answer.

Explanation

The independent variable is the factor deliberately manipulated by the experimenter, which here is temperature. The reaction rate is the dependent variable measured in response.

Question 17Nature of Science

A scientist repeats an experiment several times and obtains very consistent results, yet a colleague using a different method finds a different outcome. Which conclusion is most reasonable?

  1. Replication is unnecessary because the first results were consistent
  2. The discrepancy proves that chemistry is not a science
  3. The first scientist's results are necessarily wrong
  4. Systematic error or a methodological difference may explain the discrepancy and warrants investigation Correct answer.

Explanation

Consistent results within one method indicate precision but do not rule out systematic error specific to that method. A discrepancy across methods signals the need to examine procedure, calibration, and assumptions before drawing conclusions.

Question 18Nature of Science

Which statement about the relationship between science and technology is most accurate?

  1. Technology always precedes and never depends on science
  2. Science never benefits from technological advances
  3. Science and technology are identical pursuits with no distinction
  4. Science seeks understanding of nature, while technology applies that understanding to practical problems Correct answer.

Explanation

Science aims to build knowledge about the natural world, whereas technology applies scientific knowledge to solve practical problems. The two are interrelated, as new instruments often enable new scientific discoveries.

Question 19Nature of Science

A data table lists temperatures of 20.0 °C, 25.0 °C, and 30.0 °C. A student averages them and reports 25.000 °C. Which critique is most appropriate?

  1. The average is correct as reported because averages add precision
  2. The data cannot be averaged
  3. The average should be reported as 25.0 °C to match the precision of the data Correct answer.
  4. The average should be reported as 30 °C

Explanation

When averaging measurements, the result should reflect the precision of the original data, which here are given to one decimal place. Reporting 25.000 °C implies false precision not supported by the inputs.

Question 20Nature of Science

Which of the following best exemplifies a testable scientific question?

  1. Does the rate of a reaction change when the concentration of a reactant is doubled? Correct answer.
  2. Is blue the most beautiful color?
  3. What is the meaning of life?
  4. Should students be required to study chemistry?

Explanation

A testable scientific question can be investigated through controlled experiments and measurable data. Asking whether reaction rate changes with reactant concentration can be answered by measurement and comparison.

Question 21Nature of Science

A researcher suspects that contamination introduced by an improperly cleaned flask affected results. Which type of error does this represent?

  1. Systematic error Correct answer.
  2. A significant-figure error
  3. Random error
  4. A rounding error

Explanation

Systematic error arises from a consistent flaw in procedure or equipment, such as contaminated glassware, and shifts results in a reproducible direction. Random error, by contrast, causes scatter in both directions.

Question 22Nature of Science

Which statement best explains why scientific knowledge is described as tentative?

  1. Scientists are unsure about all conclusions
  2. Scientific knowledge is based on opinion rather than evidence
  3. Tentative knowledge cannot be tested
  4. Scientific claims are accepted only until new evidence justifies revision Correct answer.

Explanation

Scientific knowledge is provisional because conclusions are always open to revision in light of new, reproducible evidence. This tentativeness reflects the self-correcting nature of science rather than uncertainty about all findings.

Question 23Nature of Science

A chemist uses a calibration curve generated with standards of known concentration to determine an unknown. Which statement about this method is correct?

  1. The calibration curve removes the need for standards
  2. The unknown's concentration is estimated by interpolation based on the standards' measured signals Correct answer.
  3. The unknown's concentration is always exactly determined with no uncertainty
  4. The method requires no replication of measurements

Explanation

A calibration curve relates known concentrations to measured signals, and an unknown's concentration is estimated by interpolation within that range. The estimate still carries uncertainty and requires careful standards and replication.

Question 24Nature of Science

Which of the following actions would most likely be considered scientific misconduct?

  1. Reporting a result that contradicts the hypothesis
  2. Publishing methods in enough detail for replication
  3. Fabricating data to support a desired conclusion Correct answer.
  4. Revising a hypothesis after seeing unexpected data

Explanation

Fabricating data is a serious violation of research integrity because it introduces false information into the scientific record. Reporting unexpected results, sharing methods, and revising hypotheses are all legitimate scientific practices.

Question 25Nature of Science

A student uses a thermometer that consistently reads 2 °C too high for every measurement. Which statement best describes the effect on the data?

  1. The measurements are precise but systematically biased Correct answer.
  2. The measurements are both accurate and unbiased
  3. The measurements are imprecise but unbiased
  4. The measurements are random and unpredictable

Explanation

A thermometer that always reads 2 °C too high produces consistent readings, so the data are precise, but every value is shifted by the same amount, creating systematic bias. Calibration would correct this offset.

Question 26Nature of Science

A chemist proposes that a newly synthesized compound conducts electricity because it contains freely moving ions. Which statement best describes the role of this proposal within the scientific process?

  1. It is an observation that requires no supporting evidence.
  2. It is a testable hypothesis that can be evaluated by further experiment. Correct answer.
  3. It is a theory because it explains a broad class of phenomena.
  4. It is a scientific law because it predicts a measurable property.

Explanation

A hypothesis is a proposed, testable explanation for an observation, and it must be evaluated against experimental evidence. Because the proposal predicts a measurable property (conductivity), it can be tested and potentially supported or refuted.

Question 27Nature of Science

A student records the color, odor, and fizzing of a reaction mixture but does not measure any numerical quantities. Which classification of these records is most accurate?

  1. They are qualitative data because they describe non-numerical characteristics. Correct answer.
  2. They are instrumental data because a reaction occurred.
  3. They are quantitative data because fizzing can be counted.
  4. They are inferential data because they suggest a chemical change.

Explanation

Qualitative data describe properties without numerical measurement, such as color, odor, and visible bubbling. Quantitative data require numerical values obtained by measurement.

Question 28Nature of Science

A researcher wants to determine whether a new catalyst increases the yield of a reaction. Which experimental design best supports a valid conclusion?

  1. Run the reaction only with the catalyst and record the highest yield obtained.
  2. Run the reaction once with the catalyst and compare it to a published value.
  3. Run the reaction with varying catalyst amounts and varying temperatures together.
  4. Run the reaction with and without the catalyst under otherwise identical conditions. Correct answer.

Explanation

A valid causal conclusion requires comparing a treatment group with a control group while holding all other variables constant. Running the reaction with and without the catalyst under identical conditions isolates the catalyst's effect.

Question 29Nature of Science

A chemist reports a density as 2.70 g/cm³, but the accepted value is 2.70 g/cm³. Which conclusion is best supported?

  1. The result is precise but cannot be accurate.
  2. The result is neither accurate nor precise.
  3. The result is precise but inaccurate.
  4. The result is accurate for this comparison. Correct answer.

Explanation

Accuracy refers to how close a measured value is to the accepted or true value. Because the reported density matches the accepted value, the result is accurate in this comparison.

Question 30Nature of Science

A chemistry student reports a calculated volume as 24.3 mL after multiplying a measured length by a measured area. Which reasoning correctly justifies the number of significant figures?

  1. The result should always be rounded to the nearest whole number.
  2. The result should keep the same number of decimal places as the largest measurement.
  3. The result should retain as many digits as the calculator displays.
  4. The result should be limited by the measurement with the fewest significant figures used in the calculation. Correct answer.

Explanation

For multiplication and division, the result carries the same number of significant figures as the measurement with the fewest significant figures. Calculator output is not a basis for reporting precision.

Question 31Nature of Science

A scientist publishes a study, and other researchers in the field examine the methods and conclusions before the work is widely accepted. Which description best characterizes this process?

  1. Calibration, in which instruments are adjusted against known standards.
  2. Replication, in which the same experiment is repeated to confirm results.
  3. Modeling, in which a simplified representation explains the data.
  4. Peer review, in which independent experts evaluate the work's validity before acceptance. Correct answer.

Explanation

Peer review is the evaluation of scientific work by independent experts in the same field, who assess the soundness of methods and conclusions. It occurs before publication and serves as a quality-control mechanism.

Question 32Nature of Science

A researcher measures the boiling point of a liquid three times and obtains 78.1 °C, 78.2 °C, and 78.1 °C, while the accepted value is 80.1 °C. Which statement best describes these results?

  1. They are neither accurate nor precise because they differ from the accepted value.
  2. They are precise because they cluster closely but inaccurate because they differ from the accepted value. Correct answer.
  3. They are accurate because they are close to one another.
  4. They are both accurate and precise because the values are similar.

Explanation

Precision describes how closely repeated measurements agree with one another, while accuracy describes closeness to the accepted value. The three values cluster tightly, showing precision, but all lie about 2 °C below the accepted value, showing inaccuracy.

Question 33Nature of Science

A student measures the volume of a gas at several pressures while holding the temperature constant and plots pressure versus volume. Which statement best describes the resulting graph?

  1. It represents an inverse relationship because volume decreases as pressure increases. Correct answer.
  2. It represents a random relationship because pressure and volume are independent.
  3. It represents no relationship because gases are unpredictable.
  4. It represents a direct relationship because both quantities are measured in SI units.

Explanation

At constant temperature, gas pressure and volume are inversely related: as pressure increases, volume decreases. This relationship reflects Boyle's law and can be evaluated from the plotted data.

Question 34Nature of Science

A chemist suspects that a thermometer used in an experiment consistently reads 1.5 °C above the true temperature for every measurement. Which statement best describes this situation?

  1. It is a personal error because the chemist misread the scale.
  2. It is a systematic error that shifts all readings in the same direction. Correct answer.
  3. It is a random error because the readings vary unpredictably.
  4. It is not an error because the readings are consistent.

Explanation

Systematic error produces a consistent offset in one direction across measurements, often from faulty calibration. Because every reading is shifted by the same amount, the error is systematic rather than random.

Question 35Nature of Science

A researcher claims that a new drug cures a disease after observing that patients who took it recovered. Which additional consideration most strengthens the scientific validity of this causal claim?

  1. A comparison group receiving a placebo under otherwise identical conditions. Correct answer.
  2. A detailed description of the drug's chemical structure.
  3. A statement of the researcher's confidence in the result.
  4. A larger number of patients all receiving the drug.

Explanation

Establishing causation requires controlling confounding variables and comparing treatment with a control group. A placebo comparison group under identical conditions isolates the drug's effect from other factors.

Question 36Nature of Science

A published study reports a small effect that later independent studies fail to reproduce. Which conclusion about scientific knowledge is best supported by this outcome?

  1. The later studies are invalid because they contradict earlier work.
  2. The original study must have involved deliberate fraud.
  3. The original findings should be accepted because they were published.
  4. Scientific claims are provisional and may be revised when new evidence accumulates. Correct answer.

Explanation

Scientific knowledge is tentative and self-correcting; claims are revised when independent evidence fails to support them. Failure to reproduce does not by itself prove misconduct, only that the original claim is not robustly supported.

Question 37Matter and Atomic Structure

An atom of an element has 16 protons, 16 neutrons, and 18 electrons. Which statement correctly identifies this species?

  1. It is a cation of sulfur with charge 2+ and mass number 34.
  2. It is a neutral atom of argon with mass number 34.
  3. It is a sulfide ion with charge 2− and mass number 32. Correct answer.
  4. It is a neutral atom of sulfur with mass number 32.

Explanation

The number of protons fixes the element as sulfur (Z = 16), and the mass number equals protons plus neutrons, 16 + 16 = 32. With 18 electrons there are two more electrons than protons, so the species carries a 2− charge and is the sulfide ion.

Question 38Matter and Atomic Structure

Which subatomic particle determines the identity of an element while being unchanged in number during ordinary chemical reactions?

  1. Electron
  2. Proton Correct answer.
  3. Neutron
  4. Positron

Explanation

The number of protons (atomic number) uniquely defines each element, and protons are conserved in ordinary chemical reactions, which only rearrange electrons. Neutrons affect mass and isotope identity, while electrons are the particles transferred or shared in bonding.

Question 39Matter and Atomic Structure

An isotope of an element is best defined as a form of that element in which

  1. the total number of nucleons stays the same while the charge changes.
  2. the number of electrons differs while the proton number stays the same.
  3. the number of protons differs while the neutron number stays the same.
  4. the number of neutrons differs while the proton number stays the same. Correct answer.

Explanation

Isotopes of an element share the same atomic number (proton count) but differ in neutron count, giving different mass numbers. Because proton number is unchanged, isotopes are the same element and differ only in nuclear mass.

Question 40Matter and Atomic Structure

Which electron configuration represents the ground state of a neutral chlorine atom (Z = 17)?

  1. 1s² 2s² 2p⁵ 3s² 3p⁶
  2. 1s² 2s² 2p⁶ 3s² 3p⁶
  3. 1s² 2s² 2p⁶ 3s² 3p⁴ 3d¹
  4. 1s² 2s² 2p⁶ 3s² 3p⁵ Correct answer.

Explanation

Seventeen electrons fill in order of increasing energy: 1s² 2s² 2p⁶ 3s² 3p⁵, which totals 2 + 2 + 6 + 2 + 5 = 17. This configuration also matches chlorine's position in group 17 with one vacancy in the 3p subshell.

Question 41Matter and Atomic Structure

How many valence electrons does a neutral atom of phosphorus (Z = 15) have?

  1. 15
  2. 3
  3. 5 Correct answer.
  4. 8

Explanation

Phosphorus has the configuration [Ne] 3s² 3p³, so the 3s and 3p electrons together give five valence electrons. Its position in group 15 of the periodic table is consistent with a valence count of 5.

Question 42Matter and Atomic Structure

Which description correctly characterizes the Rutherford nuclear model of the atom?

  1. Atoms are indivisible spheres that cannot be subdivided further.
  2. Electrons are embedded uniformly in a sphere of positive charge.
  3. Electrons occupy quantized orbitals described by probability distributions.
  4. A small, dense, positively charged nucleus contains most of the atom's mass, with electrons outside it. Correct answer.

Explanation

Rutherford's alpha-scattering results showed that positive charge and nearly all the mass are concentrated in a tiny central nucleus, with electrons occupying the largely empty space around it. This replaced the earlier plum-pudding picture of a diffuse positive sphere.

Question 43Matter and Atomic Structure

Which pair of species are isoelectronic with each other?

  1. Cl⁻ and Ar
  2. Na⁺ and Ne
  3. Na⁺ and K⁺
  4. O²⁻ and F⁻ Correct answer.

Explanation

Isoelectronic species have identical electron counts. O²⁻ has 8 + 2 = 10 electrons and F⁻ has 9 + 1 = 10 electrons, so both have the neon configuration of 10 electrons.

Question 44Matter and Atomic Structure

Which statement best describes the modern quantum mechanical model of the atom?

  1. Electrons travel in well-defined circular orbits at fixed radii.
  2. Electrons are concentrated inside the nucleus with the protons.
  3. Electrons are fixed at the surface of a positively charged sphere.
  4. Electrons are distributed in regions of space defined by probability, called orbitals. Correct answer.

Explanation

In the quantum mechanical model, an orbital is a probability distribution describing where an electron is likely to be found; exact trajectories do not exist. This model replaced Bohr's fixed circular orbits with wavefunctions and quantized energy levels.

Question 45Matter and Atomic Structure

Which quantity increases by exactly one when moving from one element to the next across a period in the periodic table?

  1. The atomic number Correct answer.
  2. The mass number
  3. The neutron number
  4. The number of electron shells

Explanation

Moving one place to the right in the periodic table increases the atomic number (proton count) by one, which is the organizing principle of the modern table. Neutron number and mass number vary irregularly among isotopes, and shell number changes only when a new period begins.

Question 46Matter and Atomic Structure

A neutral atom has the ground-state configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. Which conclusion is correct?

  1. It is a transition metal with a half-filled d subshell.
  2. It is a noble gas with a complete valence shell.
  3. It is an alkali metal that readily loses one electron to form a 1+ ion. Correct answer.
  4. It is a halogen that readily gains one electron to form a 1− ion.

Explanation

The single 4s electron indicates a group 1 alkali metal, which characteristically loses that electron to achieve a noble-gas configuration and form a 1+ cation. The configuration shown corresponds to potassium (Z = 19).

Question 47Matter and Atomic Structure

Which element has the highest first ionization energy?

  1. Sodium
  2. Silicon Correct answer.
  3. Aluminum
  4. Magnesium

Explanation

First ionization energy increases across a period as effective nuclear charge rises and atomic radius shrinks, so the electron is held more tightly. Among the period-3 elements listed, silicon lies furthest right and has the highest first ionization energy.

Question 48Matter and Atomic Structure

Which property generally decreases from left to right across a period?

  1. Electronegativity
  2. Effective nuclear charge
  3. First ionization energy
  4. Atomic radius Correct answer.

Explanation

Across a period, added protons increase effective nuclear charge while electrons enter the same shell, pulling the electron cloud closer and reducing atomic radius. Electronegativity, effective nuclear charge, and ionization energy all generally increase left to right.

Question 49Matter and Atomic Structure

Which quantum number set (n, ℓ, mℓ, ms) is allowed for an electron in an atom?

  1. (3, 2, −2, +1/2) Correct answer.
  2. (3, −1, 0, +1/2)
  3. (1, 0, +1, −1/2)
  4. (2, 2, 0, +1/2)

Explanation

The rules require ℓ to range from 0 to n − 1 and mℓ to range from −ℓ to +ℓ, with ms equal to ±1/2. For n = 3, ℓ = 2 is allowed and mℓ = −2 lies within the permitted range, so this set is valid.

Question 50Matter and Atomic Structure

How many orbitals are contained in the 3d subshell, and what is the maximum number of electrons it can hold?

  1. Three orbitals, six electrons
  2. Seven orbitals, fourteen electrons
  3. One orbital, two electrons
  4. Five orbitals, ten electrons Correct answer.

Explanation

A d subshell has ℓ = 2, giving 2ℓ + 1 = 5 orbitals, and each orbital holds two electrons by the Pauli principle. The 3d subshell therefore accommodates a maximum of ten electrons.