The configuration about an atom can be specified through its parity attribute. This attribute, together with a general convention, determine the relative three-dimensional positioning of substituents about a central atom (Figure ). First, the parent of the central atom is identified. Then the frame of reference is shifted by sighting down the bond from the central atom's parent to the central atom. An equilateral triangle is then inscribed about the central atom. The bonds from the central atom are then iterated in order. If the parity Figure : Atom parity with one virtual hydrogen. The central atom (cyan) has a virtual hydrogen (left). In this case, the virtual hydrogen assumes the role of root atom (right). The former root atom (r) then assumes the role of the first child, and analysis continues as before.