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 CH 4 The electron configuration of C is 1s 2 2s 2 2p 2 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 sp 3

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

Boron Trifluoride Consider BF 3 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 sp 2 hybrid orbitals Notice that one p orbital is unoccupied

sp 2

sp Consider BeF 2 Electron configuration of Be is 1s 2 2s 2 Beryllium must promote one electron to the 2p orbital This results in sp hybridization and a linear shape

BeF 2 sp hybrid orbital of Be

More Information Lone pairs can occupy hybrid orbitals Consider water: it forms sp 3 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 = sp 3 3 areas of electron density = sp 2 Two areas of electron density = sp

Organic Molecules Consider ethane (C 2 H 6 ), ethene (C 2 H 4 ), and ethyne (C 2 H 2 ) Draw each Lewis structure Determine the type of hybridization each carbon has

Ethane Lewis structure: Hybridization: sp 3

Ethene Lewis structure Hybridization: sp 2

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