AP Chem · Unit 2 Progress Check

AP Chemistry Unit 2 Progress Check: Compound Structure and Properties, walkthrough only.

College Board builds Progress Check 2 from about 15 multiple-choice questions and one free-response question, and marks that free-response question Long. Unit 2 is Compound Structure and Properties, worth 7–9% of the multiple-choice section. You get the reasoning here, not an AP Classroom answer key.

Updated September 2026Written by Mahmudul HasanFree · No signup

What is on the AP Chemistry Unit 2 Progress Check

College Board publishes the composition in its Course and Exam Description, and two separate pages of it agree: the Course at a Glance table and the Unit 2 at a Glance panel.

Progress Check 2 is ~15 multiple-choice questions and one free-response question, and College Board marks that free-response question Long.

The word Long carries information. Section II of the AP Chemistry exam is built from two question types, the longer ones carrying 10 points each and the shorter ones 4, so the Progress Check is handing you the long format. College Board does not publish a point value, a time limit or a length for any Progress Check question, so treat the 10 as the exam’s figure and not this assignment’s.

Unit 2 is one of nine. The rest of the course sits in all nine AP Chemistry unit Progress Checks.

The seven topics it is drawn from

College Board numbers seven topics in Unit 2. Most study pages cover three of them, because Lewis diagrams and VSEPR are the memorable part. The solids and the energy curve are the ones that quietly turn up.

2.1 Types of chemical bonds

Ionic, covalent and metallic bonding, and what an electronegativity difference predicts about which one you get. College Board calls the ionic-to-covalent boundary a continuum rather than a line.

2.2 Intramolecular force and potential energy

The potential-energy curve against internuclear distance, which is where equilibrium bond length and bond energy come from, plus Coulomb’s law: larger charges pull harder, and so do smaller ions.

2.3 Structure of ionic solids

A particulate model of the crystal that maximizes attraction between opposite charges and minimizes repulsion between like ones.

2.4 Structure of metals and alloys

Metallic bonding drawn as a lattice of positive ions whose valence electrons are delocalized across the whole solid, then interstitial alloys, where a small atom fills the gaps, and substitutional alloys, where a similar-sized atom takes a place in the lattice.

2.5 Lewis diagrams

College Board’s name for what most classrooms call Lewis structures. Built to an established set of principles, not by eye.

2.6 Resonance and formal charge

Where several valid diagrams exist, the octet rule and formal charge are the two criteria College Board names for choosing the best model.

2.7 VSEPR and hybridization

Shape, bond angle, bond order, bond length, dipole moment and hybridization, all read off the diagram once you have it.

What Unit 2 is actually worth

College Board gives Unit 2 7–9%, and the qualifier attached to that number is the part most study pages leave off. The course description heads the table: exam weighting on the multiple-choice section. AP Central repeats the qualifier in its own column header.

The multiple-choice section is 60 questions and half the exam. Seven to nine percent of 60 works out at roughly four to five questions. That is arithmetic on two figures College Board publishes rather than a number it states, and it is a smaller claim than saying Unit 2 is 7–9% of the exam.

For the free-response section College Board publishes no per-unit weighting at all. A page that gives you one for Unit 2 has made it up.

The multiple-choice half

Most of what Unit 2 asks comes back to one chain: count the electron pairs around the central atom, use VSEPR to read off the shape, then let the shape decide everything downstream.

Electron pairs set the hybridization and the ideal angle. College Board publishes all three; lone pairs then push the real angle below the ideal one.

Two electron pairs give sp and 180°, three give sp² and 120°, four give sp³ and 109.5°. Lone pairs count as pairs even though they never appear in the shape’s name, which is why four pairs with one lone pair is trigonal pyramidal rather than tetrahedral.

Polarity then follows from the shape rather than from the bonds. A molecule can hold polar bonds and still be nonpolar when the geometry cancels the dipoles, and CO₂ is the standard case.

Bond order handles the rest. A higher bond order between the same two atoms means a shorter bond with a larger bond energy, which is College Board’s own wording.

The one free-response question

There is a single free-response question and College Board marks it Long in both at-a-glance tables. What it does not publish is the prompt, the points or the length, so anyone telling you what the question asks is guessing.

What College Board does publish is more useful. It weights six science practices per section, and Practice 3, Representing Data and Phenomena, draws no share of the multiple-choice section at all while taking 8–16% of the free-response one. AP Central shows the same split in its own skills table.

Two of Unit 2’s seven topics sit on a Practice 3 skill: topic 2.2, where the suggested skill is representing a phenomenon with a graph, and topic 2.5, where it is representing a substance with a diagram.

Read that narrowly, because it is a statement about the practice and not about the content. It does not mean Lewis diagrams are absent from multiple-choice questions. It means building a representation is not what gets scored there, so if you are going to be asked to draw one, this is where it happens.

The three mistakes College Board names

Study pages tend to list mistakes somebody thought up. College Board publishes three for this unit in its teacher guidance, and a short sourced list beats a long invented one.

Counting the valence electrons wrong

The first step, and it quietly invalidates every step after it. Nothing downstream can be right if the electron count is not.

Breaking the octet rule

A diagram that violates it is usually just the wrong diagram rather than an interesting exception.

Mixing up molecular geometry and bond angle

College Board names these as two separate things. The shape has a name, the angle has a number, and lone pairs push the real angle below the ideal one.

Two more are ours rather than College Board’s, and worth flagging as ours: reading polarity off the bonds instead of the shape, and forgetting that a lone pair is a pair. Both cost the same points as the three above.

What College Board says you do not need

This is the section worth reading twice, because it is the only one that gives time back. Unit 2 carries four exclusion statements, and each marks something the exam will not ask you.

Specific crystal structures

Knowing the arrangement of a named ionic lattice is not assessed. The particulate model is; the catalogue is not.

Where hybrid orbitals come from

The derivation and depiction of hybrid orbitals are not assessed. The sp, sp² and sp³ names are, and so is the sigma and pi distinction.

Hybridization with d orbitals

Not assessed. Once an atom has more than four electron pairs around it you are responsible for the shape and nothing else, so sp³d and sp³d² are not your problem.

Molecular orbital theory

MO diagrams, orbital filling and the bonding, nonbonding and antibonding distinction are all excluded. College Board recommends the theory for insight and then says it will not test it.

After you submit

A Progress Check is not ranked against your class and it is not a mock exam. What it returns is a rationale for every option, correct and incorrect, written by College Board. Read the rationales on the questions you got right as well, because on geometry items it is common to land on the correct shape from a wrong count.

To see what a raw score turns into, our chemistry score calculator does the conversion, and the exam review for this subject has the full format and a study plan.

Unit 3 picks up where this one stops: AP Chemistry Unit 3 Progress Check covers intermolecular forces, and College Board is careful to call those distinct from the chemical bonds you have just been working on. If the electronegativity and valence-electron work felt shaky, it comes from AP Chemistry Unit 1 Progress Check.

One thing catches people out on exam day. You are given the periodic table and an equation sheet, and the full ap chemistry formula sheet walkthrough shows what is actually on them. Almost nothing from Unit 2 is, which is the point: Lewis diagrams and VSEPR are reasoning you carry in, not values you look up.

Sources: College Board, AP Chemistry Course and Exam Description, Effective Fall 2024, for the unit weightings, the seven topics, the Progress Check composition, the exclusion statements and the science-practice tables; AP Central and AP Students AP Chemistry course and exam pages.

Frequently asked questions

Quick answers, checked against College Board.

How many questions is the AP Chemistry Unit 2 Progress Check?

College Board’s course description gives it as ~15 multiple-choice questions plus one free-response question, on two pages that agree with each other. It does not publish a time limit or a point total for any Progress Check.

Is the Unit 2 free-response question long or short?

College Board marks it Long in both at-a-glance tables. It does not publish how long the question runs, though, and you cannot infer it: the (partial) marker College Board uses for shortened Progress Check questions in some subjects appears nowhere in the AP Chemistry course description, so its absence here means nothing either way.

Do I need to know sp³d and sp³d² for Unit 2?

No. College Board rules d-orbital hybridization out of the exam outright, and adds that past four electron pairs around a central atom the shape is the only thing you are answerable for.

How much of the AP Chemistry exam is Unit 2?

Seven to nine percent, and the qualifier matters: that is the weighting on the multiple-choice section, which is 60 questions. College Board publishes no per-unit weighting for the free-response section at all.

Do you post AP Chemistry Unit 2 answers?

No, and we will not. What this page gives you is the reasoning the questions are built on and the places points go missing. College Board already writes a rationale for every option inside AP Classroom, and that is the thing worth reading.