-mixing atomic orbitals to from special orbitals for bonding
-individual atom (normally center atom in a molecule) does this
-based on how many e- areas (lone pair groups, bonds)are around the atom; for ea. e- area, one orbital added
-ex--\>O in H₂O has 4 e- areas, so: sp³
C in CO₂ has 2 e- areas, so: sp
P in PCl₅ has 5 e- areas, so: sp³d