The hybridization of a central element can be connected to its number of electron groups. When I mention electron groups, I am referring to the lone pairs on the central element plus its bonding groups, which consist of its surrounding elements. In organic chemistry, we focus on nonmetals and adhere to the octet rule, simplifying the memory process for different types of hybridization. We typically consider up to 4 electron groups. When observing two electron groups, they would display an electron geometry of linear, and its hybridization would be sp. Imagine that there is a one beside s and p. Thus, it is represented as s1p1. If we add these up, 1+1, it indicates two electron groups on the central element. With sp hybridization, s orbitals present a single spherical shape, while p orbitals group into three dumbbell shapes. Therefore, sp suggests the involvement of these two hybridized orbitals, leaving two p orbitals unhybridized.

If you have three electron groups positioned trigonally planar, the hybridization will be . Omitting the invisible number one, it can be articulated as sp2, which translates to 1+2, amounting to three electron groups. This implies that the s orbital and two of the p orbitals are hybridized, leaving only one p orbital unhybridized. Finally, four electron groups describe a tetrahedral electron geometry. The hybridization in this case is sp3, calculated as 1+3, totaling four electron groups. In this instance, all orbitals are hybridized, thus none remain unhybridized.

Let us consider an example where we draw and determine the hybridization and number of unhybridized orbitals for a covalent compound such as HCN. The least electronegative element is typically placed in the center, which would be hydrogen, but because hydrogen cannot occupy this position, carbon is centralized. Hydrogen generally forms a single bond, thus requiring only two electrons to attain a similar electronic configuration as helium. Ideally, carbon forms four bonds, and nitrogen, belonging to group 5A with five valence electrons, prefers forming three bonds. Analysis of this structure reveals that carbon, as the central element, is surrounded by two electron groups - one hydrogen and one nitrogen. These two electron groups indicate that carbon's hybridization is sp, involving the hybridization of an s orbital and one p orbital, and leaving two p orbitals unhybridized. This analysis assists in conceptualizing hybridization related to various organic molecules.