How did the development of the earliest idea about atoms differ from the later work of scientists?

The earliest ideas about atoms, which were developed by John Dalton, stated that 1) all the matter is composed of atoms; 2) atoms were indivisible tiny particles; 3) all the atoms of an element were identical, with the same size, same masses and same chemical properties; 4) the atoms of different elements were different; 5) different atoms combine is simple ratios of whole numbers to form compounds; 6) in a chemical reaction, the atoms separate or recombine to form new compounds. Nowadays, as result of the the research, most of those ideas have been modified: 1) still the matter is constituted by atoms; 2) atoms are formed by smaller particles (electrons, protons, neutrons) and they can be split; 3) isotopes are atoms of a same element that differ in the number of neutrons; 4) still atoms of different elements are different; 5) and 6) are still valid.

D=m/v =57.9/3 = 19.3 g/cm^3