Hybridization and Other Good Stuff

Introduction

• A hybrid results from combining two of the same type of objects, and it has characteristics of both

• Atomic orbitals undergo hybridization during bonding

• Consider the methane molecule

Methane

• CH4

• The electron configuration of C is 1s22s22p2

• You might expect the two unpaired p electrons to bond with other atoms and the 2s electrons to remain as a lone pair

Visual

Carbon Hybridization

• This does not happen as we know carbon forms 4 bonds

• Hybridization: a process in which atomic orbitals are mixed to form new, identical hybrid orbitals

• Each hybrid orbital contains one electron that it can share with another atom

Visual

Name of the Orbitals

• The orbitals are made from one s orbital and three p orbitals

• The name of the orbitals in methane is sp3

Geometry

• According to VSEPR, a tetrahedral shape minimizes repulsion between the orbitals

Boron Trifluoride

• Consider BF3

• VSEPR predicts a trigonal planar shape• To have this shape, one s and two p

orbitals on the boron must mix to form 3 identical sp2 hybrid orbitals

• Notice that one p orbital is unoccupied

sp2

sp

• Consider BeF2

• Electron configuration of Be is 1s22s2

• Beryllium must promote one electron to the 2p orbital

• This results in sp hybridization and a linear shape

BeF2

sp hybrid orbital of Be

More Information• Lone pairs can occupy hybrid orbitals• Consider water: it forms sp3 hybrid

orbitals and the two lone pairs on the oxygen atom are in two of the hybrid orbitals

To Determine Hybridization

• Count the total number of areas of electron density on the central atom• Be sure to include lone pairs and each bond

(whether single, double, or triple) as one area• 4 areas of electron density = sp3

• 3 areas of electron density = sp2

• Two areas of electron density = sp

Organic Molecules

• Consider ethane (C2H6), ethene (C2H4), and ethyne (C2H2)

• Draw each Lewis structure• Determine the type of hybridization each

carbon has

Ethane

• Lewis structure:

• Hybridization: sp3

Ethene

• Lewis structure

• Hybridization: sp2

Ethyne

• Lewis structure

• Hybridization: sp

Sigma Bond (σ

• Sigma bond: occurs when the electron pair is shared in an area centered between the two atoms

• The atomic orbitals (could be hybrids) overlap end-to-end

• Electron density is at is greatest on the internuclear axis (an imaginary line joining the two nuclei)

More

• Single bonds are sigma bonds

Pi Bond (π)

• Pi bond: formed when parallel orbitals overlap to share electrons

• High electron density is found above and below the inter-nuclear axis (not on it)

• A double bond consists of one sigma bond and one pi bond

• A triple bond consists of one sigma bond and two pi bonds

Comparison

Isomerism

• Isomer: species with the same formula but different properties

• The different properties are due to different arrangements of atoms

• There are two main types of isomerism: structural isomerism and stereoisomerism

Structural Isomerism

• The isomers contain the same atoms but one or more bonds differ

Stereoisomerism

• Where all the bonds in the isomers are the same but the spatial arrangements of the atoms are different

Complex Metal Ions

• Complex ion: has a metal ion at its center with a number of other molecules or ions surrounding

• Can be considered to be attached to the central ion by coordinate covalent bonds

• Ligands: the molecules or ions surrounding the central metal ion

Simple Ligands

• The most common simple ligands include water, ammonia, and chloride ions

• Coordination number: the number of ligands surrounding the central metal ion

• Some coordination numbers:• Water: 6; ammonia: 4; chloride ions: 4

Examples