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Unit 1: Atomic Structure and Properties

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How are electrons arranged in an atom, and what rules govern that arrangement?

Topic 1.5 Atomic Structure and Electron Configuration: write electron configurations for atoms and ions using the Aufbau principle, the Pauli exclusion principle, and Hund's rule, and relate them to the Coulombic model of the atom.
A focused answer to AP Chemistry Topic 1.5, covering subatomic particles, the Coulombic model, energy levels and subshells, the Aufbau principle, the Pauli exclusion principle, Hund's rule, and writing configurations for atoms and ions, with full worked examples.
11 min answer →

How do we describe and calculate the composition of a mixture, as distinct from a pure compound?

Topic 1.4 Composition of Mixtures: distinguish pure substances from mixtures and use elemental analysis and mass relationships to determine the composition of a mixture.
A focused answer to AP Chemistry Topic 1.4, covering pure substances versus mixtures, elemental analysis, mass percent of a component, and using simultaneous mass relationships to find the make-up of a mixture, with full worked examples.
9 min answer →

How do we move between the mass of a compound, its percent composition, and its empirical and molecular formulas?

Topic 1.3 Elemental Composition of Pure Substances: calculate percent composition by mass and determine empirical and molecular formulas from experimental data.
A focused answer to AP Chemistry Topic 1.3, covering percent composition by mass, empirical formulas, molecular formulas, and the mass-to-formula workflow used in combustion and gravimetric analysis, with full worked examples.
10 min answer →

How does a mass spectrum reveal the isotopes of an element and let us calculate its average atomic mass?

Topic 1.2 Mass Spectra of Elements: interpret a mass spectrum to identify the isotopes of an element and their relative abundances, and calculate the average atomic mass from the data.
A focused answer to AP Chemistry Topic 1.2, covering isotopes, the mass spectrum, mass-to-charge ratio, relative abundance, and the weighted-average calculation of atomic mass, with full worked examples.
9 min answer →

How does the mole connect the mass of a sample to the number of particles it contains?

Topic 1.1 Moles and Molar Mass: use the mole and molar mass to convert between the mass of a pure substance, the number of moles, and the number of representative particles.
A focused answer to AP Chemistry Topic 1.1, covering the mole, Avogadro's number, molar mass, and the mass-mole-particle conversions that underpin every quantitative calculation in the course, with full worked examples.
9 min answer →

Why do atomic radius, ionization energy, and electronegativity change in regular patterns across the periodic table?

Topic 1.7 Periodic Trends: explain and predict the trends in atomic and ionic radius, ionization energy, and electronegativity using effective nuclear charge and shielding.
A focused answer to AP Chemistry Topic 1.7, covering effective nuclear charge, shielding, and the trends in atomic radius, ionic radius, ionization energy, and electronegativity across and down the periodic table, with full worked reasoning.
11 min answer →

How does a photoelectron spectrum reveal the energies and numbers of electrons in each subshell of an atom?

Topic 1.6 Photoelectron Spectroscopy: interpret a photoelectron spectrum to determine the relative energies of electrons in subshells and the number of electrons in each subshell, and relate it to electron configuration.
A focused answer to AP Chemistry Topic 1.6, covering ionization energy, binding energy, the axes of a PES spectrum, reading peak position and height, and linking a spectrum to electron configuration and the Coulombic model, with full worked examples.
10 min answer →

How do valence electrons determine how an atom reacts and what ions it forms?

Topic 1.8 Valence Electrons and Ionic Compounds: relate the number of valence electrons to an element's group and reactivity, and predict the ions main-group elements form and the formulas of the ionic compounds they make.
A focused answer to AP Chemistry Topic 1.8, covering valence electrons, the link between group number and reactivity, the ions main-group elements form, and writing ionic-compound formulas, with full worked examples.
9 min answer →