Drag to rotate
Orbital energy diagram
What is hybridisation?
Mixing of atomic orbitals in an atom to generate a new set of equal-energy hybrid orbitals. Carbon first promotes a 2s electron to the empty 2p (the excited state), giving four unpaired electrons.
Count the atoms on carbon
If the C atom is directly bonded to:
• 4 atoms → sp³ (109.5°, tetrahedral)
• 3 atoms → sp² (120°, trigonal planar)
• 2 atoms → sp (180°, linear)
σ and π bonds
The first bond between two atoms is always a σ bond (head-on overlap of hybrid orbitals). Any extra bonds are π bonds, from side-on overlap of the leftover unhybridised p orbitals. See the C=C and C≡C tabs.
Single, double, triple
sp³: only σ bonds → single bonds.
sp² (ethene): 1 leftover p → C=C is 1 σ + 1 π.
sp (ethyne): 2 leftover p → C≡C is 1 σ + 2 π.