Molecules that have the same chemical formula (same numbers of each atom) but different three-dimensional shapes are called molecules that have the same chemical formula (same numbers of each atom) but different three-dimensional shapes are called functional groups isotopes hydrocarbons isomers enantiomers

The given blank can be filled with isomers.  

The isomers in chemistry refers to the molecules or ions with similar formulas, but different compositions. The isomers refer to the molecules that exhibit the same chemical formula, however, distinct three-dimensional shapes. Though isomers do not always share identical properties. The two prime forms of isomerism are stereoisomerism or spatial isomerism and structural isomerism or constitutional isomerism.  

Answer : The correct option is, Isomers

Explanation :

Isotope : It is defined as the element that have the same number of protons but have the different number of neutrons of each of the atom.

Functional groups : It is defined as they are specific grouping of atoms within the molecule that have their own characteristic properties.

For examples : alcohols, amines, carboxylic acids, ketones, ethers etc.

Hydrocarbons : It is defined as the type of organic compound that contains only hydrogen and the carbon atoms.

Enantiomers : When the two stereoisomers differ only in their arrangement of atoms and groups in space and exhibit non-superimposable object mirror image relationship.

Isomer : It is defined as a molecule have the same molecular or chemical formula but the different chemical structure or shape.

For example :

There are three structural isomers of n-hexene that is based on the location of the double-bonded carbon atoms with the other atoms.

In n-hexane, 'n' shows that the chain should be straight chain there is no branching.

The three structural isomers of n-hexene are, 1-hexene, 2-hexene and 3-hexene.

Hence, the correct option is, Isomers