Click an atom to select it, then use these or the +/− keys. Lets you build ions such as NH₄⁺ or a carboxylate.

Pick 4 bonded atoms in Measure mode to drive a dihedral angle.

Click atom — select
Drag atom — move it
Right-click atom — delete
Double-click atom — grow a neighbour
Click space — deselect
Double-click space — new atom
Alt + drag atom — draw a bond
Connect selected — touch-friendly bond creation
Click bond — cycle 1→2→3→×
Right-click bond — delete

Drag space — rotate view
Shift- or middle-drag — pan
Scroll — zoom

C O N S P F H… — pick element
G — optimize · + − — charge
Del — delete selected
Ctrl+Z / Ctrl+Shift+Z — undo / redo

Drop a .xyz, .mol or .sdf file onto the viewport to open it.

Structures that violate the octet — five-bonded carbon, two-bonded hydrogen, neutral four-bonded nitrogen — are refused as you draw, with the reason shown. Hypervalent period-3 chemistry (SF₆, PCl₅) and strained-but-real molecules (cyclopropane, cubane) remain buildable; those get advisory strain flags instead.