The length of a covalent bond varies depending on the type of bond formed. Triple bonds are generally shorter than double bonds, and double bonds are generally shorter than single bonds. Predict how the lengths of the \(C-C\) bond in the following molecules compare. a. \(C_{2} \mathrm{H}_{6}\) b. \(C_{2} \mathrm{H}_{4}\) c. \(C_{2} \mathrm{H}_{2}\)

Chemical bonding is at the heart of understanding molecular interactons and the properties of substances. It refers to the force that holds atoms together in molecules. A covalent bond, which involves the sharing of electron pairs between atoms, is one type of chemical bond that is particularly relevant to organic compounds like hydrocarbons.

When atoms with similar electronegativities come together, they often share electrons to achieve a more stable electron configuration. This sharing can occur in pairs, leading to single, double, or triple bonds—each representing a different number of shared electron pairs. A single bond is a bond in which one pair of electrons is shared, a double bond shares two pairs, and a triple bond shares three pairs of electrons.

The strength and length of these bonds play a crucial role in determining a molecule's properties and reactivity. For example, triple bonds tend to be stronger and shorter than double and single bonds due to the increased number of shared electrons pulling the atoms closer together.

The molecular structure refers to the three-dimensional arrangement of atoms within a molecule. This structure greatly influences a molecule's physical and chemical properties, such as melting and boiling points, reactivity, and polarity.

In the context of hydrocarbons, the molecular structure dictates how the carbon atoms are bonded together and to hydrogen atoms. Ethane (\(C_{2}H_{6}\)), ethene (\(C_{2}H_{4}\)), and acetylene (\(C_{2}H_{2}\)) are all composed of two carbon atoms bonded to each other and to hydrogen atoms, but the nature of the carbon-carbon bond differs in each molecule. These differences in bonding lead to different molecular geometries and, consequently, variations in physical properties such as bond lengths.

Bond length comparison is a way of understanding the relative distances between the nuclei of two bonded atoms in a molecule. This distance is affected by the bond order; higher bond orders generally result in shorter bond lengths.

Within the given hydrocarbons—ethane, ethene, and acetylene—the single, double, and triple bonds, respectively, exhibit this trend clearly. Ethane, with its single C-C bond, has the longest bond length because the bonding electrons are shared over a larger area. In contrast, the C-C bond in ethene is shorter due to the double bond that pulls the two carbon atoms closer together. Finally, acetylene features a triple bond, which is the shortest of all due to the strongest overlapping of orbitals and the highest number of bonding electrons between the carbon atoms.

Understanding bond length comparisons is crucial in predicting the behavior of molecules during chemical reactions, including their reactivity and the formation of products.