Bond energy is a measure of bond strength and is the amount of energy required to break the covalent bond. The higher the bond energy, the stronger the bond. Thus, a carbon-carbon triple bond is stronger than a carbon-carbon double bond as its bond energy is greater
Isomers are molecules that contain the same number and type of atoms, arranged in different ways. They have the same molecular formula, but can have different physical and chemical properties
These form when the atoms in molecules with the same molecular formula bond together in different arrangements. For example, when considering hexane, a carbon can be moved so that an alkyl group is formed. Or, if the molecule contains a function group, it can be moved to a different carbon and hence a different position forming an isomer.
Stereoisomers are isomers in which the atoms in two molecules are connected in the same order but have different arrangements in space. Essentially, they differ in their 3D shape and can have different chemical properties.