PLEASE HELP match the following people with their contributions to chemistry.

1. Bohr
2. Dalton
3. Mendeleev

A. Developed an atomic theory that describes the characteristics of atoms.
B. Developed the periodic table of elements format we still use today.
C. Established that electrons exist in specific energy levels using the element hydrogen.

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .

it takes on an electronical energy

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.