Contact

Mail here goes to one inbox, read by the person who writes the pages. There is no ticketing system behind it and no team to route anything to, which is the good news and the bad news at once: nothing gets lost in a queue, and nothing gets answered in an hour.

What makes a correction easy to act on

A message naming the page, the specific figure, and the reference you are checking against can be resolved in minutes. A message saying a page looks wrong somewhere takes a great deal longer, and sometimes cannot be resolved at all.

The reference matters more than you might expect. Published values genuinely differ between editions and between compilations — a density measured at 20 °C and one measured at 25 °C are both correct and are not the same number, and standard atomic weights are revised by IUPAC most years. Naming the source and its edition turns "these disagree" into a decision about which one this site should follow.

Other mail that is worth sending

• An element, comparison or concept that has no page yet. Requests are the main input to what gets written next, and a request that explains what you were trying to find out is worth more than a bare topic name.
• A page that renders badly on a particular browser, screen size or with a screen reader. Say what you were using; that detail is usually the whole diagnosis.
• Classroom and tutoring questions about the printable pack — how many copies, what counts as a class, whether a school licence is needed.

Two things that will not get an answer

Requests for advice about handling, storing, obtaining or experimenting with any substance are not answered, and no exception is made for a plausible-sounding reason. That is a fixed editorial limit rather than caution about any particular question, and the safety and accuracy notice explains where the line sits and why it is drawn there.

Link exchanges, sponsored posts, syndicated articles and offers to write a guest piece are also declined without a reply. Nothing on this site is written by anyone else, and nothing here is linked in exchange for anything.

For what the numbers are checked against before any of this starts, the methodology page names every source.