Por qué el atomismo de balton se le considera un teoría científica mientras que a leucipio y Demócrito no?

Because Democritus or Liucipius cannot demonstrate or proof their ideas as they did not have any equipment or any research to prove the existence of atoms.

Explanation:

John Dalton, Democritus and Leucipius are some of the greatest scientist and scholars of the past.

Democritus originally proposed or gave the idea of the of the composition of the matter of indivisible and tiny particles. John Dalton is credited for the beginning of the modern atomic theory.

Democritus believed that a matter is made up of atoms that can move about empty spaces. They are small, indestructible, solid, indivisible and of different shapes and sizes. Democritus proposed his idea at that time as there were no scientific advancement or instruments to prove his ideas about atoms.

Later on when science and scientific processes were advanced, Dalton was able to prove and proceed on the atomic model theory.

Democritus cannot prove his ideas as there were no instruments or advance scientific processes and so people felt his ideas as illogical. His proposals were based on his ideas.  

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.