Show errors and error tooltips
Short answer: Show errors is on by default. An amber dot marks atoms with too many bonds, or lone pairs that do not fit the charge. An amber ring marks unclear wedge or dash stereo. Hover or tap a marked atom to read the error. Turn it off in the Teaching menu.
MolDraw never stops you from drawing. When a structure breaks a rule, it marks the atom instead. This helps students find their own mistakes.
Where to find it#
- Click the Teaching button (graduation cap) in the top bar.
- Switch Show errors on or off.
- With Show errors on, switch Error tooltips on or off.
Both switches are also in Settings, General, Teaching. Both are on by default.
What is flagged#
| Mark | Problem | Example tooltip |
|---|---|---|
| Amber dot at the upper right of the atom | Too many bonds for the element and its charge | Too many bonds: C has 5 bonds, at most 4 expected |
| Amber dot | Lone pairs and formal charge do not agree | Charge does not match the lone pairs: O with 3 lone pairs here needs a − charge |
| Amber dot | More than eight electrons on B, C, N, O or F, or more than two on H | Too many electrons: N has 10 around it (3 bonds and 2 lone pairs), at most 8 |
| Amber dot | The lone pairs give a different formal charge than the one drawn | Lone pairs do not add up |
| Amber ring around the atom | Wedge and dash bonds that do not give one clear 3D arrangement | Stereo issue: the wedge and dash bonds here do not give one clear 3D arrangement |
The lone pair and charge checks run only on atoms where you drew lone pairs. Implicit hydrogens count as bonds. Atoms with a text label like Ph are not checked for lone pairs.
Error tooltips#
Hover over a marked atom or its dot to see the message. On a touch screen, tap the atom. The tooltip appears next to the atom in plain words. Turn Error tooltips off if you want students to find the problem without a hint.
The red flash while drawing#
When a new bond overfills an atom, the atom flashes red. The bond is still drawn, and the amber dot stays after the flash. This flash is not part of Show errors. To stop it, use Allow any number of bonds in Free sketch mode.
What the marks do not do#
- They never appear in downloads, copied images or print. Your exported figure stays clean.
- They do not change the structure. Fix the drawing, and the mark goes away.
Fix a flagged atom#
| Error | Fix |
|---|---|
| Too many bonds | Remove a bond, lower a bond order, or add a formal charge if the chemistry needs one. |
| Charge does not match | Add or remove a charge with the plus and minus tools, or change the number of lone pairs. See Lone pairs, radicals and charges. |
| Stereo issue | Click the wedge or dash to change it, or remove extra stereo bonds. See Stereochemistry. |
For a full check of the whole structure, use Check structure from the command palette. See Check a structure for valence errors. For the theory of formal charge, read the formal charge guide.
Questions and answers
What does the amber dot on an atom mean in MolDraw?
The atom breaks a valence rule. It has too many bonds, too many electrons, or lone pairs that do not match its charge. Hover or tap the atom to read why.
How do I turn off error marks in MolDraw?
Click the graduation cap Teaching button and switch off Show errors. Or open Settings, General, Teaching.
Will the error dots show in my exported image?
No. The marks are editor hints only. They never appear in PNG, SVG, PDF, copied images or print.
Why does an atom flash red when I add a bond?
The new bond gives the atom more bonds than its valence allows. MolDraw still draws the bond and leaves an amber dot. Turn on Free sketch mode with Allow any number of bonds to stop the flash.
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