Type of structural isomerism

Question

What is the type of structural isomerism in which isotopes move around?

Examples

1. $\ce{CH2D-NH2}$ and $\ce{CH3-NHD}$
2. $\ce{CH2D-NH-CH3}$ and $\ce{CH3-ND-CH3}$
3. $\ce{CH2D-NH-CH2CH3}$ and $\ce{CH3-NH-CHD-CH3}$ and $\ce{CH3-NH-CH2-CH2D}$

here $\ce{D}$ refers to deutrium.

My progress: So I know that there are various types of isomerism, like

1. Tautomerism - Differ in the position of protons and electrons. Usually I see that this occurs with changes in bond orders. So I don't think it will be this.
2. Ring-chain isomerism - When there is a difference in the number of carbons in a ring
3. Functional isomerism - When the functional group changes. I don't know if $\ce{-NH2}$ is a different functional group from $\ce{-NHD}$.
4. Metamerism - This is when there is a change in carbon chain on both sides of a bridging group. I don't know if a change in isotopes would count as a change in carbon chain.
5. Chain isomerism - When the carbon skeleton changes. Here the skeleton carbon is the same.
6. Positional isomerism - When a functional group attaches itself on different carbon of the same chain. Not applicable here.

This is not a homework question. This question was to fill the gap in my knowledge of isomerism with isotopes.

Answer 1

According to Wikipedia, this type of isomerism is known as Isotopomerism

Isotopomers or isotopic isomers are isomers with isotopic atoms, having the same number of each isotope of each element but differing in their positions. The result is that the molecules are either constitutional isomers or stereoisomers solely based on isotopic location. For example, $\ce{CH3CHDCH3}$ and $\ce{CH3CH2CH2D}$ are a pair of constitutional isotopomers of propane

For a different source, you can also check out the IUPAC Gold book's definition of an isotopomer.