Orbital Pictures
An orbital picture is the full set of orbitals a textbook draws on a molecule: hybrid lobes along the sigma bonds, an s orbital on each hydrogen, p lobes for the pi bonds joined by bridges, the lone pairs in their orbitals, and the shared electron pairs. Molkit builds one from the drawn structure in a single step. This page covers building a picture, its settings, how it follows edits, and how it sits in a named group. Placing single lobes by hand is covered on Orbital Lobes.
Building a picture
Select the molecule (or some of its atoms) and use any of these:
- Build All, the last button in the second row of the orbital tool’s flyout.
- Structure > Orbital Picture > Build Orbital Picture.
- Right-click the selected atoms and choose Orbitals > Build Orbital Picture.
- Build in the ORBITAL PICTURE section of the Object Properties panel.
With nothing selected, the whole drawing is used. With some atoms selected, only bonds whose two ends are both selected are drawn. The build is one undo step, and a message names anything that was left out. Building again replaces what the earlier build drew and keeps the orbitals you placed by hand.
To make a picture on a copy and leave the original drawing alone, use Derive view > Orbital picture instead (see Views and Resonance).
To build the orbital picture of ethene
- Draw ethene (two carbons joined by a double bond) and select it.
- Press
Shift+Oto open the orbital tool, then click Build All in the flyout. - Each carbon gets three sp² lobes and a p orbital. The p orbitals are joined by a bridge, each hydrogen gets an s orbital, and the bond lines under the lobes are hidden.
Press Ctrl+Z once to take the whole picture away.
What a picture draws
In a full picture, the bond lines under the lobes are hidden. With p orbitals only, the bond lines stay and stand for the sigma bonds, and a double bond between two atoms with p orbitals is drawn as one line.
A p orbital that points out of the page is drawn at an angle, and every such lobe in the picture is drawn parallel. Near lobes are layered in front of the bonds and far lobes behind. In line art (outlines only) the hidden lines are removed.
A pi system of three or more atoms (a diene, an aromatic ring, an allyl ion, a carboxylate) is drawn as one system with a bridge over every bond in it, unless Delocalized is turned off. Over benzene the bridges form a regular hexagon.
Settings for one picture
Each picture keeps its own settings. They are in the ORBITAL PICTURE section of the Object Properties panel, which appears when the selection touches a picture (and, while the hybridization tools are on, when any atom is selected). A change applies to the pictures the selection touches and redraws them in one undo step.
| Control | Choices |
|---|---|
| Preset | Valence bond, line art; Valence bond, shaded; Pi system, dashed; Pi system, dashed, line art; Pi bonds, near side; Localized pi bonds; and any you saved |
| Draw | Full picture, or p orbitals only |
| Joined by | How a pi bond joins its p orbitals: Ribbon, Single line, Dashed line, or Nothing |
| Far side | Join the far side too (on by default) |
| Pi system | Delocalized (on by default) |
| Far lobes | Hide when covered: leave out the far half of an out-of-page p orbital where the near lobes would mostly cover it (off by default) |
| Style | As the document, Line art, Flat, or Shaded |
| Ink | Colour or B & W |
| Spacing | Automatic, As drawn, Cozy (1.5 times), or Roomy |
| Letter | As the document, Lobes start at its edge, or Filled lobes run under it |
| Names | Orbital names in the lobes (on by default) |
| Pairs | Shared electron pairs (on by default); lone pairs are always drawn |
| Lock | Keep when redrawn |
A preset only fills in the controls below it. You can change any control afterwards, and the list then reads Custom. Choosing a preset leaves Ink and Spacing as they are. Save as… stores the current settings as a preset of your own, kept in this browser, and Delete removes one of yours.
Ink switches one picture between the document’s orbital colours and black and white (dark outlines and grey shading, for print).
The Structure > Orbital Picture submenu holds the same Draw, Ink, Spacing, Join p Orbitals, Join the Far Side Too, Delocalized Pi Systems and Hide Covered Far Lobes choices. There they set what a new picture starts from, and they also redraw the pictures the selection touches (every picture when nothing is selected).
Spacing
Spacing sets the bond lengths of the picture, for the whole connected structure:
- As drawn keeps the drawing’s bond lengths and sizes the orbitals to fit.
- Cozy makes the bonds 1.5 times as long as drawn.
- Roomy lengthens the bonds until every orbital name and electron pair fits.
- Automatic, the default, uses As drawn when the typical bond is at least 38 units long and Cozy when it is shorter.
Molkit remembers the length the structure was drawn with, so you can change Spacing back at any time. When the orbital names do not fit at the current bond length they are left out, and the panel says so.
Locking
Tick Lock in the ORBITAL PICTURE section to lock every orbital, bridge and shared pair of the picture on the selected atoms (the whole picture when its atoms are not selected one by one). To lock one item, select it and tick Lock in the ORBITALS section. A locked item is not changed by a redraw from a preset or another setting; it is still scaled and re-inked with its structure.
Keeping the picture in step
A picture follows its drawing. Moving an atom, changing a bond length, or changing the document’s orbital fill style, letter size or lobe-letter setting redraws it inside the same undo step. Dragging the molecule carries the picture along, and rotating the molecule as a whole turns the picture with it. A redraw discards hand edits to unlocked generated lobes.
Removing a picture
Structure > Orbital Picture > Remove Orbital Picture, the right-click Orbitals > Remove Orbital Picture, or Remove in the panel takes away everything the picture drew, locked items included. The hidden bond lines come back, a structure that Spacing lengthened returns to its drawn length, and orbitals you placed by hand stay.
Pictures in named groups
A copy of a molecule that carries an orbital picture counts as an Orbitals view. In a visual set it is labelled ORBITALS, and it is recognised also when the picture is built after the group was made. A group can hold several orbital pictures (all orbitals, the pi system only, and so on). They are alternative pictures, not resonance forms, so they get no Res box or weights. See Named Selections.
In the embeddable widget such a group shows an Orbitals button. When the group holds several pictures, numbered buttons beside it choose the picture, and a line under the picture says what it shows: All orbitals, Pi system, or a caption you wrote.