Visualisation of hybrid orbitals

In Valence Bond Theory, a chemical bond among two atoms is the result of direct overlap of two atomic orbitals (one on each atom). By a sigma bond, the overlap is along the line directly among the two nuclei. Good orbital overlap needs which the atomic orbitals on each atom (those orbitals overlapping to form the bond) be oriented in a straight line toward the other atom.

The basic s, p_x, p_y, and p_z orbitals are unsatisfactory for two purpose. First, these orbitals are not directed in a particular direction; although, they tend to spread out in all directions (or at least multiple directions). Second, to the extent in which the orbitals have an orientation (the p_x along the x axis, for instance), the geometry is frequent inconsistent along with the molecular geometry. For instance, in methane (CH₄) the carbon is at the center of the molecule and the hydrogens lie on the points of a tetrahedron. Each H-C-H bond angle is 109.5^o. The carbon 2s orbital is spherical and as such extends toward all four hydrogen atoms. The carbon 2p_x, 2p_y, and 2p_z extend along with the x, y, and z axes and as such form 90^o angles along with each other. This geometry does not provide for effectual overlap along with the hydrogen atoms.