H2O (water) has 2 hydrogen atoms and 1 oxygen atom.
A food chain is a sequence going from the producers on the bottom to the consumers to the top that shows what consumer eats what
1. combustion
2. succession
3. condensation
4. precipitation
5. pioneer species
6. decomposition
7. evaporation
8. nitrogen fixation
Pioneer species are the first species to arrive in an area after succession (hope this helped because i dont know about climax communities)