Chapter 8: Covalent Compounds: Bonding Theories and Molecular Structure

Theories of Bonding

VSEPR, Valence Bond theory, Molecular Orbital Theory

VSEPR

Valence shell electron pair repulsion Model

Charge cloud

Grouping of electrons

covalent bonds result from:

orbital overlap

How can the bonding in CH4 be explained?

when transitioning from ground-state to excited state, electron in 2s orbital jumps to 2p orbital

Atomic Orbital: (wave function)^2 =

the probability of finding an electron within a given region of space in an atom.

Molecular Orbital: (wave function)^2 =

the probability of finding an electron within a given region of space in a molecule.

Orbitals have specific:

energy levels and shapes

Orbitals can be occupied by a max of ____ electrons

2

Paired electrons in orbitals have:

opposite spins

2 ways for orbital interaction to occur according to Molecular Orbital Theory

additive and subtractive

Additive molecular orbital shape

egg

additive interaction calls σ

bonding molecular orbital

additive interaction lower in energy than:

isolated s orbitals

what causes the bond for additive interaction

Electrons spend most of their time in the region between the two nucleii

subtractive interaction shape contains:

a node between atoms

subtractive interaction Higher in energy than:

the isolated s orbitals

Electrons in subtractive interaction:

cant occupy the central region between the nuclei and don't contribute to bonding

Oxygen, O2, is predicted to be ____ by electron-dot structures and valence bond theory. However, it is known to be ____ because it is attracted to magnetic fields

diamagnetic, paramagnetic

Valence Bond Theory pros

simple

Valence Bond Theory cons

Incorrect predictions about electronic structure and Problems with resonance

Molecular Orbital Theory pros

more accurate

Molecular Orbital Theory cons

More complex

what are the eight MO's

4 bonding, 4 antibonding

Valence Shell Electron Pair Repulsion Model

Predicts molecular shapes based on electron pair repulsion.

Valence Bond Theory

Explains bonding through overlapping atomic orbitals.

Molecular Orbital Theory

Describes electron distribution in molecules using molecular orbitals.

VSEPR Model

Determines molecular geometry from charge cloud repulsion.

Two Charge Clouds

Linear

Three Charge Clouds

trigonal planar (no lone pairs), or bent (one lone pair)

Four Charge Clouds

tetrahedral (no lone pairs), trigonal pyramidal (one lone pair), or bent (two lone pairs)

Five Charge Clouds

Trigonal bipyramidal shape

Six Charge Clouds

octahedral (no lone pairs), square pyramidal (one lone pair), or square planer (two lone pairs).

Sigma Bond (σ)

Single bond formed by head-on orbital overlap.

Pi Bond (π)

Bond formed by side-on orbital overlap.

sp3 Hybridization

Involves one s and three p orbitals.

sp2 Hybridization

Involves one s and two p orbitals.

sp Hybridization

Involves one s and one p orbital.

Diamagnetic

All electrons are spin-paired, weakly repelled by magnet fields

Paramagnetic

Contains unpaired electrons, weakly attracted by magnet fields

Additive Orbital Interaction

Combines wave functions to form bonding orbitals.

Subtractive Orbital Interaction

Destroys wave functions to form antibonding orbitals.

subtractive interaction: σ* (Sigma Star)

Antibonding orbital higher in energy than σ bond.