By the end of the 19th century, more than half of the population believed in the presence of atoms.

hello your question is vague hence I will provide a general answer about what was known about atoms in the 19th Century

answer :

By the end of the 19th century more than half of the population believed in the presence of atoms and also in the 19th Century is was a known fact that atoms determine the chemical properties of an element

Explanation:

By the end of the 19th century more than half of the population believed in the presence of atoms and also by the 19th Century is was a known fact that atoms determine the chemical properties of an element.

John Dalton reintroduced the presence of atoms in 1800 with evidence which he used to develop atomic theory. with this theory people believed in the presence of atoms in nature and also that atoms determine the chemical properties of an element .

it would be c. predictability