Free sketch mode
Short answer: Click the graduation cap Teaching button and switch on Free sketch mode. MolDraw stops adding hydrogens and stops correcting valence, so you can draw any structure, even a wrong one. Pick which rules to relax in Settings, General, Teaching.
By default, MolDraw keeps your drawing chemically sensible. It adds implicit hydrogens, limits charges and trims lone pairs that do not fit. That helps most users. In a class you may want to draw a wrong structure on purpose, or let students place every electron themselves. Free sketch mode turns those rules off.
- Click the Teaching button (graduation cap) in the top bar.
- Switch on Free sketch mode.
- To choose the rules, click All teaching settings….
- In the Teaching group, switch each rule on or off.
The five rules appear in Settings only while Free sketch mode is on. All five are on by default when you start the mode.
The five rules#
| Setting | What it does | Default in the mode |
|---|---|---|
| No automatic hydrogens | Labels show only the element, O and not OH. Hydrogens appear only where you draw them. The formula counts drawn atoms only. | On |
| No valence correction | Edits never remove lone pairs or change bonds to fix valence | On |
| Allow any charge | Any atom can take a charge up to ±9 | On |
| Allow any number of lone pairs | Up to four lone pairs on any atom | On |
| Allow any number of bonds | Extra bonds are drawn without the red warning flash | On |
Turn a rule off to keep that part of the normal behaviour. For example, keep automatic hydrogens but allow any charge.
Normal limits it replaces#
- Charges: without the mode, charge tools stop at a limit per element. H and the halogens stop at ±1. C, N and O stop at ±2.
- Lone pairs: without the mode, you can place only as many pairs as the electron count allows.
- Bonds: without the mode, overfilled atoms flash red while you draw.
What still works#
- Show errors still marks atoms that break the rules. Leave it on so students see their mistakes. Turn it off for a clean sketch.
- The Lewis structure view follows the mode. With No automatic hydrogens, it shows only drawn atoms and pairs.
- With No automatic hydrogens on, the formula counts only the atoms you drew. A wrong sketch gives a wrong formula.
Ideas for a class#
- Draw a carbon with five bonds and ask students to find the error.
- Draw a bare skeleton with no hydrogens. Ask students to add every H and lone pair, then switch on Lewis structure to compare.
- Draw an unusual ion with a large charge for a discussion of stability.
Common problems#
| Problem | Fix |
|---|---|
| OH labels turned into O | No automatic hydrogens is on. Switch it off, or draw the H atoms. |
| The formula looks wrong | With automatic hydrogens off, the formula counts only drawn atoms. |
| Lone pairs disappear when I edit | Switch on No valence correction. |
Questions and answers
How do I draw a carbon with five bonds in MolDraw?
Turn on Free sketch mode in the Teaching menu. Allow any number of bonds is on by default, so the extra bond is drawn without a warning flash.
How do I stop MolDraw adding hydrogens to labels?
Turn on Free sketch mode and keep No automatic hydrogens on. An O label then stays O, and hydrogens appear only where you draw them.
What is the largest charge I can put on an atom?
In normal mode each element has a limit, such as ±2 for carbon. In Free sketch mode with Allow any charge on, any atom can reach ±9.
Does free sketch mode change saved files?
No. It changes how the editor behaves while you draw. Your structure saves as drawn.
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