Covalent bonds are formed by the overlap of atomic orbitals. As orbitals have different shapes, it is difficult to represent the actual shape of the orbitals on the paper. Hence a pictorial notation is adopted with the following rules:
- An orbital is represented by a square box (
) or a circle (O). An empty box describes a vacant orbital.
- Electrons are represented by arrows pointing upwards (h) or downwards (i) that gives the clockwise or anticlockwise spin respectively.
- Each box can accommodate at the most two electrons of opposite spins only. Single arrow represents the presence of one electron while two arrows (opposite direction) represents two paired electrons.
- The orbitals of the valence shells of the bonding atoms are shown in the order of increasing energies.
- The overlapping of the orbitals is shown by 'dashed' lines enclosing the orbitals concerned.
