In the nineteenth century, what was known about atoms?

A. The atom determines the chemical property of an element.

Atom is the smallest unit of matter which determine the chemical and physical characteristics of an element

Explanation:

During the 19th century the following was known about an atom

a) An element consists of only one type of atom.

b) Atoms cannot be created nor they can be destroyed.

c) Atom of one element differs from atom of other element

d) Atom is the smallest unit of matter

e) Two or more atoms form a compound.

f) The chemical and physical characteristics of an element is determined by the characteristics of its atom