Groups of individuals that belong to the same species and live in the same environment

This is known as Population.

Explanation:

A population is made up of organisms of the same kind living together in the same habitat. Characteristics of a population include the population size, frequency, density, percentage cover and distribution.

Factors that dominantly affect a population comes up especially in size and distribution. These factors include; migration of organisms to other habitats, invasion or colonization by new species, increase or decrease in birth and death rates etc

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.