To calculate the bond length between two carbon atoms in a molecule of ethene, we need to know the covalent radius of a carbon atom. The covalent radius of a carbon atom is approximately 77 pm picometers .Using the empirical formula for calculating bond length, we have:Bond length = sum of covalent radii of the two atomsSince both atoms are carbon, we can simply add their covalent radii together:Bond length = 77 pm covalent radius of carbon + 77 pm covalent radius of carbon Bond length = 154 pmHowever, the bond order of the carbon-carbon bond in ethene is 1.5, which means it is a combination of a single bond and a double bond. To account for this, we can take the average of the bond lengths for a single bond and a double bond.The bond length for a carbon-carbon single bond is approximately 154 pm, and the bond length for a carbon-carbon double bond is approximately 134 pm.Average bond length = single bond length + double bond length / 2Average bond length = 154 pm + 134 pm / 2Average bond length = 288 pm / 2Average bond length = 144 pmSo, the bond length between two carbon atoms in a molecule of ethene, assuming a carbon-carbon bond order of 1.5, is approximately 144 pm.