Orbital Theory, Electron Configurations, Hybridisation

What is valency?

• Atoms want a complete outer shell of electrons

• For example, carbon has 4 electrons in the outer shell, so for a full outer shell, it needs 4 extra electrons. This is done by forming covalent bonds with other atoms and sharing the bond electrons. The valency of carbon is 4.

• Valency of an atom = The number of bonds needed to complete the shell

 

sp³

• Tetrahedral

• 109.5

• All bonds are sigma

sp²

• Trigonal planar

• 120

• Bonds are single to the hydrogens, and a double bonds to carbons (sigma and pi combination)

sp

• Linear

• 180

• Sigma bonds to the hydrogens and 2 pi bonds between the carbons along with a sigma bond, making a triple bond

What’s the hybridisation in these molecules?

Sigma bonds

• Strongest type of covalent chemical bond

• Forms when atomic orbitals overlap in a head on arrangement (like two 2 s orbitals, one s orbital and one p orbital)

• σ

How does sigma bonding affect the shape and flexibility of drug molecules?

Sigma bonds = single bond from orbital overlap means free rotation

How does pi bonding affect the shape and flexibility of drug molecules?

Multiple bond from overlap of p-orbitals means fixed orientation

Double bonds in structures means there is…

restricted rotation