Final answer:
In the preparation of polyethylene from ethylene, carbon atoms change from sp² hybridization in the monomer to sp³ hybridization in the polymer.
Step-by-step explanation:
When polyethylene is prepared from ethylene, the carbon-atom hybridization changes from sp² hybridization to sp³ hybridization. In the ethylene molecule (ethene), each carbon atom is sp² hybridized, which allows for the formation of a double bond (a sigma (σ) bond and a pi (π) bond).
During the polymerization process to form polyethylene, the double bonds break, and the carbons form new single sigma bonds with adjacent carbon atoms, resulting in an sp³ hybridization which gives a tetrahedral geometry to each carbon atom in the polymer chain.
In an ethene molecule, C2H4, each carbon atom is involved in one C-C sigma bond and two C-H sigma bonds using sp² orbitals, and one pi bond formed by the side-by-side overlap of the unhybridized p orbitals on each carbon atom.