Positional isomers are characterized by:

Positional isomers are a specific type of structural isomerism where the main characteristic is that they have the same molecular formula but differ in the position of functional groups or substituents within the carbon chain. This means that while the overall number and type of atoms remain the same, the placement of these functional groups leads to different structural formulas, resulting in distinct chemical properties and reactivity.

For example, consider two positional isomers of alcohols: one may have the hydroxyl (-OH) group attached to the first carbon of the chain, while the other has it attached to the second carbon. The difference in the location of the -OH group gives each compound unique properties, even though they share the same molecular formula.

Other options address different types of variations in molecular structure. Changes in the arrangement of hydrogen atoms would indicate structural isomers, but not specifically positional isomers. The types of carbon bonds pertain to different categories of isomerism, such as bonding isomerism, rather than positional isomerism. Finally, geometric arrangement of atoms typically refers to cis-trans or E/Z isomerism, a different aspect of isomerism related to stereochemistry rather than structural characteristics.