Final answer:
Cis-trans isomers, or geometric isomers, have the same atom bonding order but different spatial arrangements. Examples for the compound CH2CH2 include cis-2-butene and trans-2-butene.
Step-by-step explanation:
Cis-trans isomers, also known as geometric isomers, are isomers in which the order of atom bonding is the same but the arrangement of atoms in space is different. One example of a geometric isomer for the compound CH2CH2 is cis-2-butene, where the two methyl groups are on the same side of the double bond. Another example is trans-2-butene, where the two methyl groups are on opposite sides of the double bond.