Past CODS Competitions

General Resources

CODS Courses (WIP)

We provide over 60 courses for all participants to use, from topics that are regularly covered in your classroom to Olympiad-specific topics. These courses are designed specifically for the chemistry Olympiad competitors and those who plan on competing in CODS Competitions. Each module provides resources, special guidance, and problems for participants to use for their learning experience. We update the courses every week and anyone can contribute to the project. Check it out!


Chemguide is a very good learning resource. Made by Jim Clark, its initial purpose was to provide U.K. students a place to learn about chemistry. However, this resource is extremely helpful for chemistry Olympiad participants as well, and the inorganic chemistry section in particular has been proven to be invaluable.


Chemistry LibreTexts

Chemistry LibreTexts can also be great help as well. Content that is present in Chemistry Olympiads that aren't taught in high school can often be learned from this website. You should check it out!



Detailed notes on competitive chemistry topics, based on Atkins Chemical Principles


Resources for U.S. Participants

Past USNCO Exams

An Invaluable resource for USNCO participants. It provides all of the past USNCO exams, and some of the more recent exams have solutions attatched to them as well. We recommend you trying these out as soon as you have covered your fundamentals!


USNCO Quizzes

Made by Andrew Ni, this resource can be useful if you would like to practice a particular topic in USNCO.


Atkin's Chemical Principles

Atkin's Chemical Principles is an invaluable textbook for not oly U.S. participants, but for all competitive chemistry learners. It is frequently used as a textbook for Honors courses in undergraduate introductory chemistry.

Resources for IChO Participants

IChO Recommendations

Written by a Gold IChO Medalist ('20) and CODS staff, Anugrah goes over what practice problems you should utilize to prepare for IChO.


Past IChO Exams

A three-part book has been made that compiles the past 50 years of ICho exams.

Past IChO Exams by Topic

A compilation of Past IChO questions by topic.


Here are some textbooks that we generally recommend for all chemistry Olympiad competitors. For more information, please refer to our introductory guide in courses.

Chemistry by Zumdahl

A very good introductory book, easy-to-understand explanations, excellent practice problems, does not cover all fo the necessary material required.

Chemical Principles by Atkins

Very good introductory book, compact explanations, decent practice problems, much more detailed than Zumdahl.

Organic Chemistry by Klein

Very good introductory book, easy-to-understand explanations, decent practice problems, provides the fundamentals of organic chemistry knowledge.

Organic Chemistry by Clayden

Very good intermediate book, outstanding explanations, outstanding practice problems, much more detailed than Klein, all you need for IChO.

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