The standard mode for whichever mouse button is the interactor (by default its the left button) is Box Select, where atoms or groups of atoms are selected by click-dragging a box on the main canvas. This and other selection types are available here.

Table 5.10. Select Toolbar Icons

	Atoms may be (de)selected by clicking on them individually, or selected en masse with a click-hold-drag
	Bound fragments are selected by clicking on a single atom within that fragment
	Clicking on a single atom selects all atoms of the same element
	The current selection is expanded by following bonds attached to any select atoms.
	Select all atoms in the current model
	Deselect all atoms in the current model
	Toggle the selection state of all atoms