IB Chemistry vocab: master key terms for exam success
11 min readOliver Kidd (Co-founder)18 Jun 2026
Mastering IB Chemistry vocab is the single most reliable way to improve your exam score. The IB DP Chemistry curriculum is built around structure and reactivity, and every concept you study is described through precise chemical language. Without that language, even correct thinking loses marks. This guide breaks down the most important terminology by syllabus area, shows you how to retain it, and explains exactly why word choice matters on your mark scheme.
1. Which IB Chemistry vocabulary terms are foundational for chemical structure?
The cumulative nature of the syllabus makes foundational vocabulary the highest-leverage place to start. If you are shaky on atomic structure, bonding, and the mole concept, every advanced topic becomes harder than it needs to be.
Core structural terms every student must own:
- Atomic number (Z): the number of protons in a nucleus, defining the element.
- Mass number (A): the total count of protons and neutrons in one atom.
- Isotopes: atoms of the same element with different numbers of neutrons, giving different mass numbers.
- Relative atomic mass (Ar): the weighted average mass of an element’s isotopes relative to one-twelfth the mass of carbon-12.
- Mole: the amount of substance containing the same number of particles as there are atoms in exactly 12 g of carbon-12, approximately 6.02 × 10²³ (Avogadro’s constant).
- Ionic bond: electrostatic attraction between oppositely charged ions formed by electron transfer.
- Covalent bond: a shared pair of electrons between two non-metal atoms.
- Metallic bond: attraction between delocalised electrons and a lattice of positive metal ions.
- Electronegativity: a measure of an atom’s ability to attract a bonding pair of electrons toward itself.
Each of these terms has a specific, examinable definition. Paraphrasing them in your own words is a common mistake that costs marks.
Pro Tip: Learn the exact phrasing used in IB mark schemes, not a loose version of the definition. Examiners award marks for specific words, so “electrostatic attraction” must appear in your ionic bonding answer, not just “attraction.”
2. What are the key terms for chemical reactivity and reaction mechanisms?
Reactivity vocabulary spans energetics, kinetics, equilibrium, acids and bases, and organic chemistry. These topics are interconnected, and linking vocabulary across syllabus units reduces confusion significantly.
Energetics and kinetics:
- Enthalpy (ΔH): the heat content of a system at constant pressure; a negative value indicates an exothermic reaction.
- Entropy (ΔS): a measure of the dispersal of energy or disorder in a system.
- Activation energy (Ea): the minimum energy required for a reaction to occur.
- Rate of reaction: the change in concentration of a reactant or product per unit time.
Equilibrium:
- Equilibrium constant (Kc): the ratio of product concentrations to reactant concentrations, each raised to their stoichiometric coefficients, at equilibrium.
- Le Chatelier’s principle: if a system at equilibrium is subjected to a change, the system shifts to oppose that change.
Acids, bases, and redox:
- Brønsted-Lowry acid: a proton (H⁺) donor.
- Brønsted-Lowry base: a proton acceptor.
- Buffer solution: a solution that resists changes in pH when small amounts of acid or base are added.
- Oxidation: loss of electrons (or an increase in oxidation state).
- Reduction: gain of electrons (or a decrease in oxidation state).
Organic chemistry:
- Nucleophilic substitution: a multistep reaction in which a nucleophile replaces a leaving group on a carbon atom.
- Electrophile: an electron-deficient species that accepts an electron pair from a nucleophile.
Knowing these definitions precisely prepares you for both short-answer and extended-response questions across Paper 2 and Paper 3.
3. How can IB Chemistry students memorise and retain complex terminology?
Active recall beats passive reading every time. Reading your notes once does not build the retrieval pathways you need under exam pressure. These methods do:
- Flashcards with exact definitions: Use Quizlet to build digital flashcard sets using mark-scheme phrasing. Quizlet’s spaced repetition algorithm surfaces cards you struggle with more frequently, which accelerates retention.
- Annotate past exam questions: When you review a mark scheme, circle every term the examiner used. Write that term into your vocabulary list with its context.
- Link vocabulary across topics: Connecting chapters like acid-base chemistry with equilibrium reveals how Kc, Ka, and buffer behaviour all share the same conceptual framework. This reduces the total number of ideas you need to memorise.
- Use official IB glossaries: Official IB glossaries provide definitions that align precisely with examiner expectations. These are the definitions worth memorising.
- Practise lab work: Hands-on practical activities solidify theoretical terms by giving them real context. Seeing a buffer in action makes the definition stick far better than reading it.
Pro Tip: A Casio graphical calculator with a pre-installed periodic table gives you fast access to element data during revision sessions, saving time when checking Ar values or electron configurations.
4. How does precise IB Chemistry terminology affect your exam score?
Vague language costs marks even when your underlying chemistry is correct. Examiners follow mark schemes that specify exact terms, and a near-miss answer receives zero for that point.
The table below shows common language errors and their precise replacements:
| Vague or incorrect term | Precise IB term required |
|---|---|
| “Energy is released” | “Enthalpy change is negative (exothermic)” |
| “The reaction speeds up” | “The rate of reaction increases” |
| “Particles move faster” | “Particles have greater kinetic energy” |
| “The solution becomes more acidic” | “The pH decreases” |
| “Electrons are shared” | “A shared pair of electrons forms a covalent bond” |
Each substitution above represents a mark. Across a full Paper 2, these small corrections add up to a meaningful grade difference. Dedicated revision glossaries phrased for IB mark schemes are one of the most efficient tools for closing this gap. The IB Chemistry study guide from Tibertutor also maps vocabulary directly to exam skills, which makes it easier to see where your language is letting you down.
Precise terminology also matters in scientific communication beyond the exam. Writing clearly and correctly is a skill that carries into university-level chemistry and research.
Key takeaways
Mastering IB Chemistry terminology requires learning exact mark-scheme phrasing, linking vocabulary across syllabus topics, and practising active recall consistently.
| Point | Details |
|---|---|
| Start with foundational terms | Atomic structure, bonding, and the mole concept underpin every advanced topic. |
| Use mark-scheme language | Write “enthalpy” not “energy” and “rate of reaction” not “speed” to secure marks. |
| Link vocabulary across topics | Connecting equilibrium with acid-base chemistry reduces confusion and aids retention. |
| Practise active recall | Flashcard tools like Quizlet with spaced repetition build retrieval under exam pressure. |
| Use official IB resources | IB glossaries and past mark schemes give you the exact definitions examiners reward. |
Why vocabulary is the quiet difference-maker in IB Chemistry
I have worked with hundreds of IB Chemistry students, and the pattern is consistent. Students who plateau at a 5 almost always have the right ideas. What they lack is the language to express those ideas in a way the examiner can credit.
The IB Chemistry syllabus is built on structure and reactivity as twin organising ideas. Once you see vocabulary as the language of that relationship, rather than a list of isolated definitions, everything clicks into place. A student who understands that “electronegativity” explains polarity, which explains solubility, which explains reaction mechanisms, is not memorising three separate facts. They are building one coherent picture.
The most common pitfall I see is leaving vocabulary revision too late. Students spend weeks on calculations and then cram definitions in the final fortnight. That approach works for formulas. It does not work for language. Vocabulary needs time to settle, to be used in context, and to be retrieved repeatedly before it becomes automatic. Start your IB Chemistry terminology work in the first month of the course, not the last.
— Oliver
Build your IB Chemistry vocabulary with Tibertutor
Tibertutor is built by IB examiners who know exactly which terms appear on mark schemes and how to phrase definitions for maximum credit.
The IB Science Questionbank gives you thousands of exam-style questions mapped to the current syllabus, with mark schemes that show you the precise language examiners reward. Every question is an opportunity to practise your terminology in context, not just recall it in isolation. Tibertutor also offers flashcards, cram sheets, and detailed notes, all aligned to IB DP Chemistry. If you want structured, examiner-quality support for your IB Chemistry exam prep, Tibertutor is the place to start.
FAQ
What is IB Chemistry vocabulary?
IB Chemistry vocabulary is the set of precise technical terms defined by the IB DP Chemistry syllabus. These terms describe chemical structures, reactions, and properties in the exact language required by IB examiners.
Why do I lose marks for using the wrong words?
IB mark schemes award marks for specific phrases. Writing “energy” instead of “enthalpy” or “speed” instead of “rate of reaction” does not match the mark-scheme criteria, so the mark is not awarded.
How many key terms do I need to know for IB Chemistry?
The IB DP Chemistry syllabus covers hundreds of terms across structure, reactivity, and practical skills. Prioritise the definitions that appear most frequently in past paper mark schemes, particularly in energetics, bonding, and equilibrium.
What is the best way to learn IB Chemistry definitions?
Active recall using flashcard tools like Quizlet, combined with annotating past exam mark schemes, is the most effective method. Linking definitions across topics, such as connecting Le Chatelier’s principle with buffer chemistry, deepens understanding and aids long-term retention.
Where can I find official IB Chemistry definitions?
The IB publishes official chemistry resources including subject guides and data booklets that contain authoritative definitions aligned with examiner expectations.