Question

Summarize the five points of Dalton’s atomic theory, and explain at least one change that occurred to the atomic theory because of further experimentation.
Important Points:
All matter is composed of very small particles called atoms.
All atoms of a given element are identical.
Atoms cannot be created, destroyed, or subdivided.
Atoms combine with or separate from other atoms.
Atoms combine with each other.

Answer 1

Five points of Dalton's atomic theory:
1) all elements are made up of atoms. 
2) atoms are so small that they cannot be divided any further. 
3) an atom can neither be destroyed nor be formed. 
4) atoms of an element are similar, they posses same mass and same properties. 
5) atoms of different elements combine in a definite ratio to form compounds. 

Due to further experimentation it was concluded that atom is made up of small particles identified as proton, neutrons, and electrons. They can be further subdivided.

Another change is the presence of isotopes of atoms of different elements. Hence, atoms of the same element can also have different masses.