Terms of Use
Last reviewed 30 July 2026.
Using this site means accepting what follows. It is short because the site does very little: it serves pages, it runs calculators in your browser, and it sells one file.
Facts are free; the writing is not
The physical data here — melting points, atomic weights, isotopic abundances, configurations — are measurements published by NIST, IUPAC and PubChem. Facts of that kind belong to nobody, and nothing on this site attempts to claim them. Take any number you need.
The prose is a different matter. Every page of explanation, every comparison and every essay was written for this site and is protected by copyright. The reasonable use of it looks like this:
- Quote a paragraph in an essay, a lesson, a forum answer or an article, with a link back. No permission needed and none will be refused.
- Show a page in a classroom, or point students at one. Also fine, also unnecessary to ask.
- Do not republish pages in whole or in substantial part, on another site, in an app, in a printed product, or as training material presented as your own.
- Do not scrape the corpus wholesale. Reading the site with a browser is what it is for; systematic automated retrieval of every page is not, and may be blocked.
The printable pack
Buying the study pack buys a licence to use it, not ownership of it. That licence runs to the individual who paid, covers unlimited printing for their own teaching, tutoring or study, and does not extend to redistributing the PDF itself — to colleagues, to a school intranet, to a file-sharing site or to students as a download. An institution wanting a copy for shared internal use should ask, and will be told yes on sensible terms.
Delivery is by email after payment clears. If the file does not arrive, or arrives corrupted, say so and it will be resent; a delivery failure is never treated as a completed sale. Because the product is a download that cannot be returned once opened, refunds are given where the pack is not what was described, where it will not open, or where a purchase was plainly made in error and the file has not been used — and requests are read by a person rather than a policy engine. Updated versions are provided to existing buyers at no charge for as long as the pack is maintained.
No warranty, and what that actually means here
Considerable effort goes into the accuracy of every figure, and the sourcing behind each one is set out on the methodology page. None of that amounts to a guarantee. Data is transcribed from published references and references contain errors; snapshots go out of date; calculators round. The site is provided as it is, without warranty of any kind, express or implied.
You are responsible for verifying anything that matters before you rely on it. Nothing here may be used as the basis for handling any material, and the reasons for that are set out in the safety and accuracy notice, which forms part of these terms.
To the fullest extent the law allows, no liability is accepted for loss arising from the use of this site or of anything obtained through it — including a mark lost on an examination, a calculation that went wrong, or a decision taken on a number read here. Where liability cannot be excluded, it is limited to the amount you have paid, which for almost every reader is nothing.
Links out, and changes in
Pages here link to external references, standards bodies and archives. Those sites are not under any control exercised here and their content is their own responsibility.
These terms may change as what the site does changes. Material revisions move the date at the top. If any part of this is found unenforceable, the rest continues to apply.