Athanor by arbastro
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Why an atom is flagged

The badge at the bottom left of the canvas counts problems in what you drew, such as a carbon with five bonds (an error) or a stereocenter with no wedge (a warning). Click it to see the list. Athanor flags problems and never changes your structure on its own.

What the badge says

The badge at the bottom left of the canvas reads No issues while everything is valid. When Athanor finds something, it shows a symbol and a count instead.

The issues badge showing one problem at the bottom left of the canvas.The issues badge showing one problem at the bottom left of the canvas.

See the problems

Click the badge. The list opens with counts for errors, warnings and notes, a Search problems box, and one row per problem, such as C has 5 bonds.

The issues list with one error: C has 5 bonds.The issues list with one error: C has 5 bonds.

Common problems

An atom has too many bonds

A carbon takes four bonds, nitrogen three (four when it carries a positive charge), oxygen two. Remove a bond, or add the charge if you meant an ion: point at the atom and press + or -.

A stereocenter's configuration is not drawn

A warning, not an error: the structure has a stereocenter with no wedge or hash. Draw one if the configuration matters. See How to draw wedge and hash bonds.

Why Athanor does not just fix it

A drawing that looks wrong may be exactly what you meant: a carbocation, a radical, a transition state. Changing it silently would hide a mistake in some drawings and introduce one in others, so Athanor shows the problem and leaves the choice to you.

Names, properties and checksHow to check a structure for errorsSelect the structure and press Shift+K (Check structure). Athanor lists each problem it finds, such as a carbon with five bonds, with a suggestion. A clean structure gets "No problems found.Switching from ChemDrawWhat works differently from ChemDrawAthanor saves as you work, flags valence and stereo problems instead of silently changing your structure, shows actions for the selection in a bar beside it, and finds commands by ChemDraw's names in Search everything.

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Last updated Nov 12, 2026