Genetic drift tends to occur in populations that

are reproductively isolated

Explanation:

The genetic drift represents a change in the frequency of an already existing gene variant in a population as a consequence of random sampling of organisms. The offspring would have the genes from their parents, and because the population is limited in numbers and it has been exposed to a new environment, the individuals with advantageous traits will survive and reproduce, while the others will die out gradually. This occurs when a small population of some species is reproductively isolated. The genetic variation is very small because of the small number of individuals, so only certain genes are passed on tot he offspring, thus resulting in gradual changes that will eventually lead to the creation of a separate species.

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds