If you are already on your study of chemistry journey you will know that it is a complex subject that can sometimes even be overwhelming, especially if you are learning in a classroom situation. Students can get left behind easily which is problematic when, like mathematics, one concept builds on the other for progression to occur.

The unique phrases and words associated with the study of chemistry can also add to its challenges. This article aims to provide a guide to the most important chemistry terms. These are not only essential for students but even the chemists, engineers, and professors who use them. These are terms that will crop up as you begin to prepare for exams by looking at chemistry past papers and your chemistry formula sheet. In fact, these words and definitions could end up unlocking a whole new world for you and most certainly add new meaning to your chemistry notes.

Whether you are a high school chemistry student or preparing for a university entrance exam, this glossary of terms should be as handy to you as your chemistry formula sheet or the periodic table.

Fundamental Terms for the Study of Chemistry

It’s always helpful to start at the beginning. The study of chemistry basically comprises understanding atoms, molecules, elements, and compounds – these four terms, which actually make up everything in the universe, are the very basics in terms of understanding chemistry terminology. If you are making chemistry notes, start here:

Elements: an element like iron or oxygen is a pure substance that cannot be broken down into another substance. It can only be broken down into atoms, or indeed the smallest fraction of the element, while still recognising it as an element. So a good way of understanding an element is that it is many parts of the same atom.

Molecules: molecules are simply two or more atoms joined (or bonded) to each other. As an example, an oxygen atom would not be a molecule, however if two oxygen atoms bond, it forms a molecule known as O2.

Compounds: when a molecule has a bond between two different types of atoms it is called a compound. For example, if you added a carbon atom to 0² - you would get carbon dioxide also known as CO- this is a compound.

Before moving on, make sure that you always have a chemistry formula sheet at hand which would be divided up into stoichiometry; acids and bases; electrochemistry, and gas laws.

Breaking it Down Further: More Basic Chemistry Terms

books stacked in rows
As a chemistry student, you will need to understand specific terminology. - Source: Unsplash

To understand how atoms bond, we need to understand their breakdown even further. As you will know from your study of chemistry, atoms, which are made of particles can either clump together in the atom’s nucleus or actually spin around that nucleus. The particles, which have a charge, are either positive, neutral, or negative. The atom’s centre, called the nucleus holds protons, these have a positive charge while the neurons are neutral. Meanwhile, negatively charged electrons orbit the nucleus.

(By the way, remembering a concept like this, which is key to understanding how compounds and molecules are made is helpful in diagram format, which is why your chemistry notes should be filled with colourful diagrams that will help you).

Atoms will bond with each other because of these electrons and there are two types which should be included in your chemistry notes:

  • Covalent bonds: this is when two atoms share one or more pairs of electrons
  • Ionic bonds: this is when an atom actually donates an electron to another. When this happens, the atom that was donated becomes an ion, which means it is positively charged. Metals are elements that by nature lose electrons, form bonds, and develop positive charges.

Learning all of this in parrot-fashion style is one thing, but truly grasping an understanding of the study of chemistry is another. This is why so many students, even those who have diligently taken chemistry notes or pored over chemistry past papers on their own opt for a chemistry tutor to help them outside of their classroom situation and ordinary syllabus. If this sounds like you, consider a website like Superprof that could very well host a chemistry tutor near you. If not, you could consider signing up for online chemistry lessons with a chemistry tutor from much further afield.

Key Vocabulary for Chemical States and Compounds

So far we have covered basic chemistry terms, but here are a few words that might help you to make more sense of that chemistry formula sheet or indeed, chemistry past papers.

Firstly, molecules that make up substances can be found in one of three states. And while you may have come across these, it’s important to remember that substances change due to heat and pressure. Here are the three substance states worth adding to your chemistry notes.

  • Gases: these are substances with no definable volume or shape.
  • Liquids: fluid in nature, these substances have definite volume, but no shape.
  • Solids: more stable in nature, solids have tightly packed molecules and therefore a more fixed shape as well as definite volume.

Substances can be pure compounds, elements, or mixtures. In the study of chemistry, a mixture can be defined as a substance that is made of two or more elements combined, yet not chemically bonded like in the case of a compound.

There are three different types of compounds:

  • Hydrocarbons: this is an organic compound containing only hydrogen and carbon.
  • Polymers: this is a large molecule, formed by lots of smaller bonded molecules (hydrocarbons) and can be naturally occurring or synthetically produced in a lab.
  • Salt: this is an ionic compound that has a neutralised charge and combines positively charged ions with negative ones.

Finally, there are acids and alkalis which are opposite in nature. Acids donate protons, contain hydrogen, and when in water, make positive ions. Alkalis in water will produce negative ions. This is one of those topics that a chemistry tutor could take you through in a lot more depth.

Terminology for Chemical Processes and Reactions

If you are a Grade 11 or Matric chemistry student, you will need to know the basic terminology associated with chemical reactions. Add these three to your chemistry notes, or glossary of terms.

note paper, pen and badges
be sure to add important terms and concepts to your chemistry notes. - Source: Unsplash

The reactant: this is the substance that is present at the start of every reaction.

The catalyst: this is the substance that will enable the reaction but not be changed by it.

The product:  this is what you get as a result of the reaction.

Also, every reaction is either exothermic, which means it gives energy away, or endothermic which means it takes in energy.

Here is an important table on the main types of reactions to add to your chemistry notes or glossary.


OxidationA reaction involving oxygen where an electron is lost.
DistillationThis occurs after a mixture has lost liquid through evaporation or condensation.
ReductionThis happens when electrons are added to atoms, which is the opposite of oxidation.
TitrationUsed to establish the concentration of a solution, when you know the concentration of a different solution.
Thermal DecompositionThis occurs when a compound is broken into two or more substances through heating.

Language Terms for Measurements and the Periodic Table

Making great chemistry notes and understanding terminology is important, but equally, so you need to understand how a chemist will measure or calculate a given substance. Explaining this kind of terminology is something you could ask of your chemistry tutor to help you better understand in class:

  • The Periodic Table: Every chemistry lab has one! Elements are arranged according to their atomic number on a table. As important as your chemistry formula sheet, this is an invention by Mendeleev, one of the world’s most famous chemists.
  • Atomic Number: This is made up of the number of protons in an atom – and its equal amount of electrons.
  • Mass Number: The number of protons and the number of neurons.
  • Transition Element: The elements contained in groups 3-12 of the periodic table are also called transition metals.
  • Mole: A unit of measure for an amount of substance.
  • Reactivity: Relative reactivity is concerning how reactive one substance is to another. When you put substances in order of their reactivity to another it is called reactivity series.
  • Chemical equation: Alongside every reaction, there is a chemical equation that shows in written form which reactants were used and what product was products were produced.
  • The pH scale: Ranging from 0-14, this describes the range of acid or alkali present in a substance. A high acidic content will have the lowest number, while a high alkali content will have the highest number, neutral has a pH7.

Important Chemistry Equipment Terms

Your chemistry notes or glossary should have a list of equipment terminology including the following.

Bunsen Burner: used for heating plugging into gas

Tripod and gauze: a stand which holds beakers filled with solutions

Test tube: a slim tube used for performing experiments

Burettes: similar to test tubes, but with measurements and clamps

Finally, remember that all of life is chemistry in action, and your choice to invest further in the study of chemistry to bring all of this language to life, will never be wasted.

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Niki is a content writer from Cape Town, South Africa, who is passionate about words, strategic communication and using words to help create and maintain brand personas. Niki has a PR and marketing background, but her happiest place is when she is bringing a story to life on a page.