hybrid orbitals. why covalent bonds exist atoms share electrons when their orbitals overlap when...
TRANSCRIPT
Why Covalent Bonds Exist
Atoms share electrons when their orbitals overlap
When orbitals overlap, electrons are simultaneously attracted to both nuclei
Bond Length
As atoms come closer, increasing electron density results in a decrease in potential energy of system
As atoms become very close, electrostatic repulsion between nuclei increases
Bond distance is a compromise between increased overlap drawing them together and increased repulsion pushing them apart
There is an optimal bond distance where energy is lowest
Sigma Bond (σ)
Covalent bond which the electron density is concentrated symmetrically along the internuclear axis
Line joining the two nuclei passes through middle of overlap
Could be two s orbitals overlap, two p orbitals overlap or an s and p overlap
Pi Bond (π)
Overlap of orbital is perpendicular to line connecting nuclei
Two p orbitals overlapping Since not a total overlap pi bonds tend
to be weaker than sigma
Bond Types Single bonds are always sigma Double bonds consist of a sigma and a
pi bond Triple bonds, sigma and two pi
Hybrid Orbitals
Mixing of s and p orbitals creates hybrid orbitals
CH4 has four bonds coming from central atom
Each bond is formed by overlap of an sp hybrid orbital
Types of Hybrids
sp3 hybrid – one s and three p orbital joined
sp2 hybrid – one s and two p orbitals sp hybrid – one s and one p orbital Hybrid orbital type accounts for
observed geometry
Predicting Hybrid Orbitals
Draw structure Determine electron pair geometry Specify hybrid orbitals needed to
accommodate the electron pairs