Difference Between Pure and Hybrid Orbitals

The key difference between pure and hybrid orbitals is that the pure orbitals are the original atomic orbitals whereas the hybrid orbitals form from the mixing of two or more atomic orbitals.

In the chemical bond formation of simple molecules, we can simply consider the overlapping of atomic orbitals. But if we are to discuss the chemical bonding in complex molecules, we need to know what is orbital hybridization. Orbital hybridization is the chemical concept that describes the mixing of atomic orbitals to form new hybrid orbitals. These orbitals involve in the formation of covalent chemical bonds.

CONTENTS

1. Overview and Key Difference
2. What are Pure Orbitals
3. What are Hybrid Orbitals
4. Side by Side Comparison – Pure vs Hybrid Orbitals in Tabular Form
5. Summary

What are Pure Orbitals?

Pure orbitals are atomic orbitals that contain electrons of the atom. These orbitals are not mixed orbitals like hybrid orbitals. The orbital gives the most probable location of electrons in an atom since the electrons are in continuous movement around the atomic nucleus. Rather than a fixed location, this gives a region where the electron can occur at a particular time.

The pure atomic orbitals exist in several shapes such as spherical shape, dumbbell shape. According to the quantum mechanics, there is a set of quantum numbers that we use to name an orbital. This set of numbers include n (principal quantum number), l (angular momentum quantum number), m (magnetic quantum number) and s (spin quantum number). Each orbital occupies a maximum of two electrons. According to the angular momentum quantum number, there are four commonly known atomic orbitals as s orbital (spherical shaped), p orbital (dumbbell-shaped), d orbital (two dumbbells in the same plane) and f orbital (a complicated structure).

What are Hybrid Orbitals?

Hybrid orbitals are the molecular orbitals that form from the mixing of atomic orbitals. These are hypothetical orbitals. The mixing occurs between the atomic orbitals of the same atom. this mixing occurs in order to form a covalent chemical bond with another atom. The process of this mixing is “orbital hybridization” which results in hybrid orbitals. We name these orbitals according to the atomic orbitals that undergo hybridization.

Accordingly, the three main forms of hybrid orbitals are:

1. sp hybrid orbital – this forms due to the hybridization of s and p atomic orbitals. Therefore the resulting hybrid orbital has 50% s characteristics and 50% p orbital characteristics. This hybrid orbital has a linear spatial arrangement.
2. sp² hybrid orbital – this forms due to the hybridization of one s and two p orbitals. Therefore the resulting hybrid orbital has 33% of s orbital characteristics and 66% of p orbital characteristic. The spatial arrangement is trigonal planar.
3. sp³ hybrid orbital – this forms due to the hybridization of one s and three p orbitals. Hence the resulting hybrid orbital has 25% s characteristics and 75% p characteristics. The spatial arrangement of these hybrid orbitals is tetrahedral.

What is the Difference Between Pure and Hybrid Orbitals?

Pure orbitals are atomic orbitals that contain electrons of the atom whereas hybrid orbitals are the molecular orbitals that form from the mixing of atomic orbitals. This is the key difference between pure and hybrid orbitals. Furthermore, the hybrid orbitals form via orbital hybridization, but pure orbitals are not hybridized. Moreover, the formation of hybrid orbitals is important in the formation of complicated chemical compounds via formation of covalent chemical bonds. When considering the nomenclature of orbitals, we name pure orbitals as s, p, d and f orbitals while we name hybrid orbitals as sp, sp², sp³, etc.

The below infographic tabulates the difference between pure and hybrid orbitals for quick reference.

Summary – Pure vs Hybrid Orbitals

Atomic orbitals are the regions where electrons exist in atoms. In this article, we described two types of orbitals as pure and hybrid orbitals. The key difference between pure and hybrid orbitals is that pure orbitals are the original atomic orbitals whereas hybrid orbitals form from the mixing of two or more atomic orbitals.

Reference:

1. Libretexts. “Hybrid Orbitals.” Chemistry LibreTexts, Libretexts, 21 July 2016. Available here  

Image Courtesy:

1.”AE4h”By Jfmelero – Own work, (CC BY-SA 3.0) via Commons Wikimedia