AP Exam Prep · AP Chemistry
AP Chemistry Unit 1 Practice Test: Atomic Structure and Properties
Unit 1 connects counting particles to the structure of atoms. You need to convert between mass, moles and particles, read mass spectra and photoelectron spectra, and explain periodic trends with Coulomb's law.
- Exam weighting:
- 7–9%
- Questions:
- 12 multiple choice
- Time:
- about 16 minutes
- Cost:
- Free, no sign-up
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What AP Chem Unit 1 covers
Unit 1, Atomic Structure and Properties, makes up 7–9% of the multiple-choice section and usually takes ~9–10 class periods. These are the topics in the current course framework, and every question in the test above is tagged with one of them.
- 1.1Moles and Molar Mass
- 1.2Mass Spectra of Elements
- 1.3Elemental Composition of Pure Substances
- 1.4Composition of Mixtures
- 1.5Atomic Structure and Electron Configuration
- 1.6Photoelectron Spectroscopy
- 1.7Periodic Trends
- 1.8Valence Electrons and Ionic Compounds
Unit 1 key ideas
The mole links mass and particles
Molar mass converts grams to moles, and Avogadro's number (6.022 × 10²³ mol⁻¹) converts moles to particles. Always track units through each step.
Composition reveals formulas
Mass percentages give the empirical formula: convert each percentage to moles, then divide by the smallest number of moles. Mixtures can be analysed the same way.
Electrons fill shells and subshells
Electron configurations follow the order of subshell energies. Photoelectron spectra show each subshell as a peak: its position gives binding energy and its height gives the number of electrons.
Coulomb's law explains trends
Attraction grows with nuclear charge and falls with distance. Across a period, effective nuclear charge rises, so radius falls and ionization energy rises; down a group, extra shells increase radius.
Common Unit 1 mistakes
- Multiplying by molar mass when you should divide (grams ÷ g/mol = mol).
- Forgetting that ionization energy dips from N to O because of paired-electron repulsion.
- Reading a PES peak height as energy instead of electron count.
How to study this unit
- Write units on every number in a mole calculation and cancel them as you go.
- When explaining a periodic trend, name the factor (nuclear charge, distance or shielding) and connect it to Coulomb's law.
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More AP Chemistry practice tests
- Unit 1 · 7–9%Atomic Structure and Properties
- Unit 2 · 7–9%Compound Structure and Properties
- Unit 3 · 18–22%Properties of Substances and Mixtures
- Unit 4 · 7–9%Chemical Reactions
- Unit 5 · 7–9%Kinetics
- Unit 6 · 7–9%Thermochemistry
- Unit 7 · 7–9%Equilibrium
- Unit 8 · 11–15%Acids and Bases
- Unit 9 · 7–9%Thermodynamics and Electrochemistry
About these questions
StudyCoach wrote these questions for this test. Each one is mapped to a topic in the College Board's current AP Chemistry course framework. Every answer key was also checked by a separate AI review, and any disagreement was rechecked by hand. They have not yet been reviewed by an AP Chemistry teacher. If you think an answer is wrong, email support@studycoach.io.
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