Microchem
Microscale Chemistry Experimentation for Teachers

22. C₂H₆ orbital model (sp³ hybridization)
Two methane molecules are modelled by using black and white beads for C and H atoms and golden and white microbeads for bonding pairs of electrons. The two models are placed top-to-top like the blue paper tetrahydra are.
In each of the two methane molecules the tetrahedral set of four sp³ orbitals of the carbon atom are used to  bond to the H atoms to form four equivalent C-H bonds.
 

One ethane molecule is modelled by using 2 black and 6 white beads for the 2 C and 6 H atoms.  Micobeads of different colours are models of bonding pairs of electrons:
Only three of four sp³ hybrid orbitals of each carbon atom are used to bond to three H atoms to form three equivalent C-H bonds. The fourth sp³ orbital of each C atom is used to form a C-C bond.