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Why Copying and Pasting Chemical Equations Can Break Formatting

Hidden characters, common sources, and how to avoid formatting errors

TL;DR — Copying and Pasting Equations

  • Copying and pasting equations can introduce hidden formatting characters

  • These characters may prevent the Chemical Equation Editor from interpreting your input

  • When this happens, the equation may be reported as not a valid chemical equation

  • Retyping the equation manually is often the fastest and most reliable fix

Why Copying and Pasting Causes Problems

When you copy text from another source, you’re not just copying what you can see on the screen. Many programs include extra formatting information that isn’t visible but still affects how the text is interpreted.

For chemical equations, this can cause problems because the Chemical Equation Editor relies on plain text symbols to understand chemical structure. If hidden characters are present, the editor may not be able to correctly interpret your equation—even if it looks chemically correct to you.

Common Sources of Hidden Characters

Hidden or non-standard characters are especially common when copying equations from:

  • PDFs

  • Word processors or slide decks

  • Online textbooks or websites

  • AI tools (including ChatGPT)

  • Notes apps or formatted documents

These sources often use visual formatting (such as superscripts, subscripts, or special symbols) that does not translate cleanly into plain text.

Examples of What Can Go Wrong

Copy-pasted equations may include:

  • Superscripts or subscripts that look correct but are not plain text

  • Invisible characters inserted between symbols

  • Mixed formatting within the same equation

When this happens, the Chemical Equation Editor may display the equation but report that it is not a valid chemical equation due to a formatting issue.

This does not usually mean your chemistry is wrong—it means the formatting cannot be interpreted reliably.

How to Fix Formatting Issues

If an equation isn’t being accepted after copying and pasting:

  1. Retype the equation manually directly into the editor

  2. Use plain text formatting:

    • _ for subscripts

    • ^ for charges

    • ->, <->, or <=> for reaction arrows

  3. Check the interpreted equation and any messages shown below the input box

In many cases, simply retyping the equation resolves the issue immediately.

If you’re not sure which formatting to use, see How to Enter Chemical Equations in Stemble for a step-by-step guide to correct equation entry.

When Retyping Doesn’t Help

If retyping the equation doesn’t fix the problem:

  • Try entering the equation in smaller parts

  • Remove and re-add symbols one at a time

  • Double-check spacing between species and symbols

If the issue persists, contact support and include:

  • Your course name

  • The assignment name

  • The task number

This information helps support identify the issue more quickly.