Charges

Formal charges are stored on the atom and drawn as a small marker next to its label. You apply them with the Charge tool or keyboard shortcuts, choose between superscript and circled styles, and reposition the marker by dropdown or by dragging. Charges also feed Molkit’s chemistry: they change implicit hydrogen counts and are checked by structure validation.

Adding a charge

Select the Charge tool in the toolbar (the +/- icon). Clicking the button opens a flyout with eight presets: +, -, 2+, 2-, 3+, 3-, and circled plus and minus. Right-clicking the button opens the same flyout without switching to the Charge tool. Pick one, then click an atom to apply it.

Clicking the same atom again with the same charge and style removes the charge, so the tool works as a toggle. Clicking a different preset onto an already-charged atom replaces the value.

Clicking empty canvas creates a standalone charge annotation you can place freely, useful for net-charge labels on brackets or reaction schemes.

Keyboard shortcuts

With one or more atoms selected, press + (or =) to increment the charge and - to decrement it. Values are clamped to the range -6 to +6, and the shortcut applies to every selected atom at once. Decrementing through zero removes the marker and clears any per-atom display overrides.

Display styles

Two styles are available: Superscript (plain +, 2-, etc. raised beside the label) and Circle (the symbol inside a circle). The document-wide default lives in the Structure Settings dialog under the Charges tab, along with default size, position, and X/Y offsets. Applying a charge with a style that differs from the document default records a per-atom override; applying one that matches clears the override so the atom follows the global setting again.

Charge Properties panel

Click an existing charge marker with the Charge tool to open the Charge Properties panel (Molkit switches to the Select tool automatically). The panel offers:

Charge: a combo box with common values plus free text. Typing 2+, 3-, ++, or -- parses both the value and a custom display text, so you can show repeated plus signs instead of 2+ if you prefer.
Style: Superscript or Circle, per charge.
Color: a color picker with hex input and a reset button.
Size: a multiplier slider from 0.3 to 3 (default 0.85). Double-click the slider to reset.

While the panel is open for an atom, pressing Delete removes that charge.

Positioning the marker

By default the marker is placed automatically near the atom label. To override it, select the atom and open the Object Properties panel; the Charge section has a Position dropdown with Auto, Top Right, Top Left, Top Center, Bottom Right, Bottom Left, and Bottom Center.

For exact placement, drag the marker itself. While dragging, alignment guides snap the charge to the edges and center of the atom label. Dragging sets the position to Custom with a stored offset; the marker then moves with the atom.

Effect on chemistry

Charge enters the implicit hydrogen calculation, so a nitrogen with a + charge picks up a fourth hydrogen and a deprotonated oxygen drops one. Structure validation also compares your drawn charge against the computed formal charge and raises a warning when they disagree, which catches missing lone pairs or wrong bond counts. See Validation.